7 Money Mistakes Almost Every Teenager Makes (And How to Avoid Them)

I'm 17. I've made most of these mistakes myself. Some of them I caught early, some of them I learned about by watching people around me mess up, and a few of them I'm still working on. I'm not writing this from some perfect-finances high horse — I'm writing it because nobody told me this stuff and I had to figure it out the hard way.

If you're a teenager or in your early twenties, here are the mistakes that will cost you the most money over your lifetime — and most of them have nothing to do with investing.

## Mistake 1: Spending everything you make

This is the big one. When you get your first paycheck and you have basically no bills, it feels like all of that money is spending money. And in a way it is — nobody's going to stop you from blowing your entire check at the mall or on food with friends.

But here's what nobody tells you: this is the **only time in your life** when you have income and almost zero expenses. Once you're 22 and paying rent, car insurance, phone bills, groceries, and everything else, saving money gets dramatically harder. The easiest money you'll ever save is right now, while someone else is paying for your housing and food.

I'm not saying don't spend anything. You're a teenager, enjoy your life. But if you're making $800 a month and spending $800 a month, you're wasting the single best wealth-building window you'll ever have.

**The fix:** Pay yourself first. When your paycheck hits, immediately move a set percentage — even 20% — into savings or investments before you spend anything. Whatever's left is your fun money. This way you never have to think about whether to save because it already happened.

## Mistake 2: Not opening a bank account (or using a bad one)

Some teenagers keep all their money as cash. In their room. In a drawer. Maybe in an envelope.

This is a problem for two reasons. First, cash is incredibly easy to spend. When it's sitting right there, every impulse purchase is frictionless. Second, cash doesn't grow. At all. A hundred dollars in your dresser today will still be a hundred dollars in five years — actually less, because inflation will have eaten some of its purchasing power.

Other teens open a bank account but don't pay attention to the fees. Some banks charge monthly maintenance fees, overdraft fees, ATM fees — they'll nickel and dime you if you let them.

**The fix:** Open a free checking account and a high-yield savings account. Lots of online banks (like Marcus, Ally, or even some credit unions) offer savings accounts paying 4-5% interest with no fees and no minimums. Your money should be earning something, even if it's just sitting there as your emergency cushion.

## Mistake 3: Thinking investing is only for rich people

I talk to people my age about investing and the most common response is some version of "I don't have enough money for that." They picture investing as something you do with $10,000 or $50,000 — something for adults with real salaries.

Meanwhile you can open a Fidelity account right now and invest $1. One dollar. Into the same index funds that billionaires use. There is no minimum anymore. The barrier to entry is literally zero.

The math doesn't care if you start with $50 or $50,000. Compound growth works the same way at any amount. The only thing that matters is time — how long your money has to grow. And right now, as a teenager, you have more time than any other group of investors on the planet. That's your actual advantage, not the dollar amount.

**The fix:** Open a custodial investment account (or a Roth IRA if you have job income) and start with whatever you have. Even $25/month. It'll feel pointless at first. It's not. I break down the actual math in my post on [how much a teenager should invest].

## Mistake 4: Getting into dumb debt early

Credit cards, buy-now-pay-later apps, financing a car you can't afford — these are traps that are specifically designed to look harmless to young people.

Credit cards aren't inherently bad. In fact, building credit early is smart. The problem is when you carry a balance. Credit card interest rates are typically 20-30%, which means if you put $1,000 on a card and only make minimum payments, you'll end up paying back $1,300 or more. You're literally paying extra money for the privilege of buying something you couldn't afford.

Buy-now-pay-later apps (Afterpay, Klarna, etc.) are the same thing dressed up in a friendlier package. They train you to spend money you don't have and normalize debt as a normal part of buying stuff. It's not. If you can't buy it outright, you can't afford it — with very few exceptions.

**The fix:** If you get a credit card (and you should eventually, for the credit history), use it only for things you'd buy anyway and pay the full balance every single month. Never carry a balance. Never. Treat it like a debit card that builds your credit score. And stay away from buy-now-pay-later for stuff you don't need — if you have to split a $40 purchase into four payments, that's a sign you shouldn't be buying it.

## Mistake 5: Ignoring your credit score

Your credit score follows you for your entire adult life. It affects whether you can rent an apartment, what interest rate you get on a car loan or mortgage, sometimes even whether you get a job (some employers check credit). And it takes years to build, so starting early matters.

Most teenagers don't think about their credit score at all because it feels like an "adult thing." Then they turn 22, want to rent their first apartment, and realize they have no credit history, which is almost as bad as having bad credit. Landlords and lenders want to see that you've borrowed money and paid it back reliably, and if you have zero history, they have no reason to trust you.

**The fix:** The easiest way to start building credit as a teenager is to become an authorized user on a parent's credit card (their good payment history transfers to your credit file). Once you're 18, open your own credit card — a secured card is the easiest to get approved for — and use it for small purchases like gas or groceries. Pay it off in full every month. Your score will build steadily over time without you doing anything special.

## Mistake 6: Following financial advice from social media

This one is everywhere and it's getting worse. TikTok and Instagram are full of people who look successful giving financial advice that ranges from oversimplified to flat-out dangerous.

"This one stock is about to explode." "I made $10,000 in a week doing this." "Drop shipping will make you rich." "Buy this crypto before it moons." You've seen these. They're almost always either misleading (they're showing you the one win and hiding the ten losses), selling you something (a course, a Discord group, a signal service), or both.

The most boring financial advice is almost always the best. Buy index funds, spend less than you earn, avoid dumb debt, start early. Nobody's making viral content about that because it doesn't get clicks. But it's what actually works.

**The fix:** Be extremely skeptical of anyone promising fast or guaranteed returns. If it sounds too good to be true, it is. Get your financial education from books (The Simple Path to Wealth is a great starting point), reputable sources (Investopedia for definitions, Bogleheads wiki for strategy), and communities where people are genuinely trying to help each other rather than sell something.

## Mistake 7: Waiting to start

This is the most expensive mistake on the list and it doesn't feel like a mistake at all. It feels responsible. "I'll start investing when I have a real job." "I'll figure out finances when I'm older." "I don't know enough yet." These all sound reasonable, and they'll cost you hundreds of thousands of dollars.

Here's the math one more time because it's that important:

**Person A** starts investing $150/month at age 18 and stops at 28 (invests for only 10 years, then never adds another dollar).

**Person B** starts investing $150/month at age 28 and continues until age 65 (invests for 37 years straight).

At a 7% average annual return, Person A — who invested for only 10 years and then stopped — ends up with **more money** at 65 than Person B, who invested for 37 years. Person A contributed $18,000 total. Person B contributed $66,600.

Person A wins because their money had more time to compound. That's it. That's the whole secret. The 10-year head start was worth more than 27 extra years of contributions.

Every year you wait to start is a year of compounding you can never get back. You can always earn more money later. You can never get more time.

**The fix:** Start today. Not "soon." Not "when I know more." Today. Open an account, put in $20, buy an index fund. Learn as you go. You will never feel perfectly ready and that's fine. Done is better than perfect, and early beats everything.

## The uncomfortable truth

Most of these mistakes come from the same place: nobody teaches us this stuff. Schools don't cover it in any meaningful way. A lot of our parents never learned it either. So we end up figuring it out at 25 or 30 after we've already lost years of potential growth and possibly taken on dumb debt.

The fact that you're reading this at all means you're already ahead. Most teenagers aren't thinking about money beyond their next paycheck. You're thinking about compound interest and Roth IRAs and credit scores. That puts you in a tiny minority, and 10 years from now, the gap between you and everyone who started late is going to be enormous.

Don't waste the head start.

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*Want more stuff like this? I write one post a week about personal finance from a student's perspective — real talk, no fluff. Check out [How Much Should a 17-Year-Old Actually Invest?], [Index Funds Explained], [What Is a Roth IRA?], and [How to Start Investing With $100]. Or subscribe to get them in your inbox.*