Money doesn't ask how you paid. But the price tag on these sneakers is about to change depending on what's in your hand at checkout.

• Cash
• Debit
• Buy now, pay later, split into 4
• Credit card, paid off in full
• Credit card, carried for a while

(3 of these cost exactly $180. The other 2 don't. Guess which.)

Somebody fronts you the money. You owe it back on a schedule. That's credit, whatever it's called and however it shows up.

You just sorted out what you've actually used. Here's why the same $180 purchase doesn't always cost $180.

A late fee is a flat charge for missing a payment date. It hits once, whether you're a day late or a week late.

Interest is a different thing. It's an ongoing charge for carrying a balance instead of paying it off. The longer you carry it, the more it adds up.

Some of these charge nothing for being late. You won't know which one you signed up for until you read the terms. And credit cards carry late fees too: the real number shows up on a real offer in Lesson 2.

Documented income means a lender can verify it: a pay stub, a tax form, something on paper. Not a promise.

Under 21, federal law requires documented independent income or a cosigner before a bank will give you a credit card. Sort these 4 into whether they count.

What's something you bought in the last month that you'd pay for differently after that first activity?

What you picked up:

• Buy now, pay later is credit. You've probably already used it.
• A card paid in full costs exactly what you spent. Carry a balance and the price changes.
• Documented income is what a lender actually checks, not what feels like a job.