Three Principles of Personal Finance: All You Need to Know for Financial Success

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More than 10,000 books have been written about personal finance. You could spend a lifetime reading them. Some of them are great1; others are 99% motivation, 1% actual, actionable information2. The truth is personal finance is simple. Every one of these books can be reduced into three basic principles:

  1. Spend less than you earn
  2. Make the money you have work for you
  3. Be prepared for the unexpected

While the principles might sound like common sense, the real trick is to truly understand them, and more importantly, to apply them.

Our Stance: was founded to make personal finance simple, understandable, and ultimately life-enhancing. Money, after all, is a means to an end. It’s a tool for doing more, and having more time. It’s not just about increasing your net worth or saving for retirement. As we say at Mint, money is for living.

Spend Less Than You Earn

Put another way, “spend less than you earn” means: live within your means, don’t overspend, don’t get yourself into debt and start saving. Easy to say, not so easy to do — especially given the appeal of a new car, a sweet home theater, a couple nights each week out with friends, and a posh tropical vacation every once in a while.

However, setting up a budget and checking in with your spending on a regular cadence is key. Creating a budget doesn’t have to be complex; budgeting methods such as the 50/30/20 rule make it easy to get started. This rule stipulates that you spend:

  • 50% of your monthly income on essentials
  • 30% of your monthly income on wants
  • 20% of your monthly income on savings

Try our calculator; simply put in your monthly income (after taxes), and see how much you have to funnel into each category of purchase.

50/30/20 Budget Calculator
Here’s how much you have for:
Monthly after-tax income


Consider Big Spending Decisions, and Plan Accordingly

Creating to and sticking to your budget is the first step, but what about those big purchases? You know, the big decisions that significantly affect your expenses (and therefore your ability to save for other things) more than anything else. These are the areas where you need to go in understanding the costs involved, so that you come out remaining financially strong.

1. Buying a House

A house is likely the most expensive purchase you’ll ever make. And it’s not just the mortgage, its property taxes, home owner’s insurance, maintenance, and the time it takes to mow the lawn. Too many people think that buying a home is automatically a good investment, since you’re “not throwing money away on rent.”

While owning a home of your own may be the American dream, it doesn’t always make economic sense. If you live in California, the Northeast, or Southwest where housing prices have doubled or tripled in the last 10 years, it’s almost always better to rent and invest the difference (more on this in principal #2).

Even if you live outside those regions, if you move within the next five years (and if you’re in your 20s that’s almost a certainty), the closing costs and 6% realtor fees will eat away your gains. By contrast, if you plan to stay in the same area indefinitely, a house may be one of the best investments you make.

To determine what’s right for you, I like the NY Times Rent vs. Buy Calculator. It’s the best one on the web, and easy to use: just enter your rent and the price to buy a comparable place3.

Rent vs. Buy Calculator

2. Kids (and when to have them)

Children can be an amazing source of joy in your life. If you’re planning to have some, it’s important to realize the expense involved, so you can make the best decision on when to do so. Kids mean more money spent on a bigger house, a bigger car, food, clothes, healthcare, and education. The cost of raising a child calculator at BabyCenter does a good job of breaking things down by region and household income level. In today’s dollars, most estimates approach $200,000 per child (excluding college). That’s about $11,000 per year per child.

This cost can be lessened dramatically by waiting a few years. If you wait to have kids for 4 years, and instead invest that $11,000 per year at a 10% return, you would have $67,000 by time your child is born. As you begin to take $11,000 per year out for child-related expenses, part of your original investment continues to grow. In the 18 years spent raising your child, you will expend only $100,000 out of pocket. It’s like having a child at half the cost.

3. Where you live

You probably choose where to live based on job opportunities, proximity to family and friends, or a great climate. But where you live has a big impact on how much you can save.

For example, if you make $75,000 a year in Austin, you would need to make $135,000 in San Francisco to maintain your lifestyle. That’s an 80% increase in cost of living. Unfortunately, moving from Austin to San Francisco, salaries typically increase by only 30%.

To compare major cities, I like BankRate’s cost of moving calculator. It shows the difference in housing costs, doctor’s appointments, and even the cost of a haircut.

4. Car (new or used)

Automobile manufacturers and dealers spent more than $15 billion in 2007 to convince you to buy a new car4. Seriously, that’s billion with a “b”. Let’s say you cave and decide to get a 2009 Chevy Malibu because it will “only” cost $21,000. Three years later, the car has depreciated by $8,000 and you’ve paid more than $3,000 in finance charges – a total expense of $11,000. If you bought a used 2005 Malibu instead, depreciation and finance charges add to only $3,500. That’s a $7,500 difference. You can see the calculation yourself at Edmunds.

Maybe you want something better than a Malibu. Buy a 2005 BMW 545i for $28,000 instead of the 2009 550i for $60,000. It will cost $32,000 less to buy used, and you’ll save $25,000 in depreciation and finance charges over the next 3 years. Always buy used, even if only last year’s model (I myself own a ’94 and a ’96). Impressing the neighbors (or the ladies) with an ever so slightly better model probably isn’t worth it. Getting Ahead in Your Savings

Easy Ways to Maximize Your Savings

Beyond the “big four” financial decisions, there a few things everyone can do to maximize savings. And they can all be done without radically altering your lifestyle.

Get a credit card that pays you:

Always use a credit card – instead of a debit card, checks or cash – if you pay off your balance in full each month. A credit card gives you a 30-day interest free loan, more rewards, and in conjunction with a tool like Mint, better visibility into exactly where your money goes.

Turn the tables on your credit card company and make them pay you with a rewards card. Whether you opt for points, miles, or cash back is up to you, but don’t settle for anything less than 1% back (or 1 point or mile per dollar).

Usually, you can do much better. Discover® More Card with $50 Cash Back Bonus offers 5% cash back in categories like travel, home improvement stores, gas, restaurants, and groceries, and up to 1% on all other purchases. Capital One® No Hassle Miles℠ Rewards earns you 1.25 miles for every dollar spent on purchases.

The catch is that most cards offering 3-5% cash back have a cap on rewards. Keeping track of all the restrictions, and calculating whether it’s better to get cash back on restaurants or utilities is difficult. Fortunately, Mint does all that work for you. Based on your unique spending categories, Mint finds the card that maximizes your rewards.

If you carry a balance on your credit card, maximizing your rewards is secondary. Paying down your debt comes first. A $5,000 credit card bill paid off at a $100 minimum monthly payment takes 9 years to pay off. In that time, you will have spent $5,100 in interest charges alone!

If you switch to a 0% introductory rate card (and keep switching when the introductory rate expires), that $100 a month payment means you’ll be debt free in less than half the time.

Upgrade your bank account:

This year, US banks are expected to charge consumers over $55 billion in fees5. To add insult to injury, the average savings account pays you only 0.50% interest (and most checking accounts earn no interest at all).

Banks work by accumulating deposits, then loaning that money out as a mortgage or to a business. Those loans are paid back at an interest rate that is typically around 5.00% ~ 8.00%. If the average bank pays you only 0.50%, they’re taking that difference as profit — profits that could go to you. Get a savings account from Ally Bank or Capital One that pays much more.

Better rates, better savings. Why settle for 0% from your checking or 0.50% from your savings? When compared to an account at 0.50%, a savings of $20,000 in a 5.00% account can earn you an extra $1,000 per year!

Upgrade your bank. Here are high-yield accounts for your checking and savings.

Checking: E*Trade Max-Rate Checking Account
Savings: Ally Bank

Get a lower price on your bills:

No one likes to overpay, but most of us do. Are you sure you’ve got the best price for your internet, TV, or mobile phone service? Probably not. New plans, equipment, and promotional rates come out every day.

Frequently, the biggest savings come from bundling multiple services together. By switching to Comcast or AT&T you can get phone, TV and internet all for about $100 a month (including taxes and fees). That can save an average household $300-$800 each year.

A dollar saved is many dollars earned:

Lower prices on everyday bills, a credit card that pays you, and a bank account that earns maximum interest add up. On Mint, we’ve found that the average household can save nearly $1,800 each year. If you start when you’re 30, investing that savings at a 10% return means $569,000 by age 65. And that leads us to our next topic: the power of compound interest.

Try our compound interest calculator.


  • Consciously weigh the financial impact of buying vs. renting, when to have kids, & where you live.
  • Buy your cars used.
  • Get a credit card like Discover® More Card with $50 Cash Back Bonus or Capital One® No Hassle Miles℠ Rewards that pays you back with cash or miles.
  • Pay off your credit cards, highest interest first.
  • Put your savings in a high-yield account like Ally Online Savings Account.
  • Use Mint to manage your finances and find a lower price on your monthly bills


Notes & References:

  1. My favorite personal finance books are:
  2. Rich Dad, Poor Dad is particularly guilty here. In my opinion, while popular, it is largely fluff with only one specific, actionable suggestion: buy real estate as an investment and rent it out.
  3. Under the “General” settings for the Rent vs. Buy Calculator, you should try these settings: increase your investment return from 5% to 10%, and income tax rate from 20% to 35%.
  4. Source: TNS Media Intelligence.
  5. Robert Hammer of investment banking firm R.K. Hammer, cited in MSN Money.

Make the Money You Have Work for You

Make The Money You Have Work For You

If you saved $10,000 a year for the next 40 years and earned no interest, you would have $400,000. If you invested $10,000 a year and earned a 10% return each year, you would have $5,267,155. Why the difference? Because your interest earns interest, and its interest earns interest, and so on. The result is exponential growth. Remember calculus? This time it actually works for you.

To obtain real wealth, you need to redeploy your money. And that means investment. It’s how capitalism works. You can put your money into stocks where you own a part of a corporation; bonds where you loan your money out and earn interest in return; real estate; or start your own business. Managing real estate can be a full time job, and owning your own business certainly is. Since both of these may require radical changes in life style, we’ll ignore them to focus on investments open to everyone: stocks and bonds.

Stocks vs. Bonds:

Over the last 200 years, stocks have consistently and reliably outperformed bonds. Not counting inflation, stocks have averaged 10% a year; and 14% for the past 20 years. Accounting for inflation, stocks have provided a “real” return of 7% annually, doubling their value every 7 years. By contrast, bonds have produced an average real return of 4.5%, doubling only every 16 years1.

For money you need in the next four years, stocks may not be the right choice. In the short term, the market may swing widely up or down. You can lose money. In the long term, however, a portfolio weighted heavily in stocks has consistently outperformed one weighted towards bonds or other fixed-income investments (such as CDs or money market funds).

Individual stocks are risky. Any one company might go out of business, suffer an accounting scandal, or miss their quarterly earnings. To distribute your risk (or in investment terms “diversify your portfolio”), buy a mutual fund. But be aware of the big differences between those that are “actively managed” vs. “indexed”.

Some mutual funds are actively managed by professionals. This active trading comes with a cost: management fees, administrative fees, and transaction costs can eat up to 2% of your investment each year. Active trading also means more taxes in the form of short term capital gains. Are they worth the cost? Often, they’re not: 80% of mutual funds under-perform the S&P 500 index.

You should also be aware that choosing the right mutual fund is nearly as hard as choosing the right stock. By contrast, index funds are “passive” – these funds invest in specific set of stocks designed to simply mirror the market instead of trying to out-guess it. The result: fees at index funds like the Vanguard S&P 500 are less than 0.20% annually.

Pay Yourself First:

You pay the government. You pay your rent (or mortgage). You pay your bills. How about paying your (future) self for change? They key is to do it automatically, every paycheck, before you get a chance to spend or even see the money. If your company has a 401k plan, start contributing. This money comes out of gross-pay and is not taxed. Even better, companies often “match” employee contributions. You put in $1, they put in $1; it’s like doubling your money immediately. Even if you company matches only $0.50 to the dollar, that’s still an instant 50% return.

If your company does not have a 401k (or you’ve maxed it out), you can setup “automatic” investments with E*Trade, Fidelity, Vanguard, and most major brokerages. Each month, they’ll take $1,000 from your checking account, and put it towards the investment (hopefully an index fund!) of your choosing.

The Magic of Compound Interest:

The end result of automatic monthly investments: wealth that grows year after year.

Monthly Investment Age Total Invested to age 65 7% 10% 13%
$100 20 $54,000 $379,259 $1,048,250 $3,096,741
25 $48,000 $262,481 $632,408 $1,617,907
30 $42,000 $180,105 $379,664 $843,184
35 $36,000 $121,997 $226,049 $437,327
40 $30,000 $81,007 $132,683 $224,709
$200 20 $108,000 $758,519 $2,096,500 $6,193,482
25 $96,000 $524,963 $1,264,816 $3,235,813
30 $84,000 $360,211 $759,328 $1,686,368
35 $72,000 $243,994 $452,098 $874,654
40 $60,000 $162,014 $265,367 $449,418
$500 20 $270,000 $1,896,297 $5,241,251 $15,483,705
25 $240,000 $1,312,407 $3,162,040 $8,089,533
30 $210,000 $900,527 $1,898,319 $4,215,920
35 $180,000 $609,985 $1,130,244 $2,186,635
40 $150,000 $405,036 $663,417 $1,123,546
$1,000 20 $540,000 $3,792,595 $10,482,502 $30,967,409
25 $480,000 $2,624,813 $6,324,080 $16,179,066
30 $420,000 $1,801,055 $3,796,638 $8,431,839
35 $360,000 $1,219,971 $2,260,488 $4,373,270
40 $300,000 $810,072 $1,326,833 $2,247,092

Think you’ll be a millionaire? Be wary of taxes. Instead of a 10% return, taxes knock it back to 7%. If you’re 30, that means your $500 a month investment drops from $1,898,319 to $900,527. But there is a way to avoid taxes; it’s called an IRA (Individual Retirement Account).

Like a 401k, an IRA allows your money to grow tax-free until you take it out for retirement. Unfortunately, if you need to money before retirement, you’ll be hit with penalties and be forced to pay the extra taxes. A better alternative, especially if you’re young, may be a Roth IRA. Contributions to a Roth IRA are made from after-tax income. As a result, you can withdraw your original contributions at any time, penalty and tax-free. By “avoiding taxes” and investing small amounts every month, anyone can achieve financial security.


  • Weigh your long term portfolio heavily towards stocks.
  • For money needed in less than four years, keep it in a high-yield savings account, money market fund, or CD.
  • Invest $100-$1,000 a month automatically into index funds or the closest alternative offered by your company’s 401k plan.



  1. See “Stocks for the Long Run” by Jeremy Siegel, Chapter 1.

Prepare for the Unexpected

The best laid financial plan can be quickly ruined by a streak of misfortune: job loss, fire, theft, or health problems. You need to protect yourself, but it’s not nearly as hard as you think.

Emergency Fund:

Without savings, living paycheck-to-paycheck leaves you vulnerable. You need a buffer, a way to get back on your feet if disaster strikes. Save enough for at least three months’ expenses. For most people, that should be $10,000-20,000. This is savings separate and distinct from your vacation fund and your investments. It’s your “open in case of emergencies only” fund.

Build your emergency fund.

Earn rates much higher than that of the national average. Just pay careful attention to the minimum balance require to avoid fees; amount required to open account; and amount required to maintain yield.

Accelerate your emergency fund. Here are two accounts that offer competitive rates.

Ally Online Savings Account
CapitalOne Online Savings Account


Yes, if you’re an adult, you need insurance. And no, not just car insurance. What you need depends on where you are in life. Medical bills are cited in about half of all bankruptcies1. And it’s no wonder. Break your leg rock-climbing and you could be stuck with a $5,000+ bill. If your company doesn’t provide it, you need health insurance.

If you’re in your twenties or early thirties, choose an inexpensive plan with a high deductible. You want something to protect you from disaster, but without breaking the bank. In most states, you can find a plan with a $2-3,000 deductible for $50-100 per month. You may not have the prescription drug benefits, or the low co-pay of those $300 per month plans, but if you only go to the doctor once or twice a year, you’ll come out way ahead.

If you rent, you need renter’s insurance. Sadly, only about 33% of renters actually buy this coverage2. Renter’s insurance protects you against fire, theft, and most natural disasters. Step back and think about how much it would cost to replace your computer, TV, couch, bed, and everything else you own. With renter’s insurance, you can get $20k in coverage for only $10-15 a month. It’s dirt cheap and worth it.

Renter’s insurance also protects you outside your apartment. If your car window is smashed and someone grabs your laptop, your car insurance will only cover the window, not the laptop. A good $20,000 renter’s insurance policy would give you up to $2,000 to replace your loss. Keep in mind that roommates’ possessions are not covered; your roommate needs a policy of his or her own.


  • Save $10-20k in an emergency fund. Keep that fund in a high-yield savings account like Ally Bank or Capital One.
  • If you need health insurance, consider a $50-$100 a month high-deductible plan. Being without health insurance leaves you too vulnerable to bankruptcy or worse.
  • If you rent, get rent’s insurance. It’s only $120-$160 per year.



  1. “Illness and Injury as Contributors to Bankruptcy”
  2. “Millions of Renters Lack Insurance

Financial Success in Three Steps:

We’ve now reduced personal finance to three simple principles, and no more than a dozen action items. But where do you start right now?

1. Use Mint…and see where your money goes

The first step to financial success is to know where you stand. You need a complete picture of how much you have, how much you owe, and where it’s all going. With Mint, you get all of that – for free, and with less than five minutes of setup.

2. Pay off your credit cards (highest rate first)

We’ve already shown you that a $5,000 credit card bill paid off at $100 a month will take nine years and $5,100 in additional interest charges. If you’re paying 20% interest on credit card debt, action item number one is to pay it off before you do anything else. There’s no point investing your money at a 10-15% gain, when it could be used to avoid a 20% loss.

3. Setup automatic investments

The key to wealth is compound interest. Invest just $200 every month when you’re 25 and at a 10% return, you’ll have $1.2m by 65. You’ll also have savings in case of emergency, money for your children’s college, and the ability to borrow from your investments for a down-payment on a house.

Not sure you can find $200 a month? Mint shows the average user over $1,800 in annual savings – that’s $150 a month right there. You’ll be well on your way.


Written by Mint

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