Good debt vs. bad debt

The financial internet loves to say 'all debt is bad.' That's cleaner than the truth, which is that debt is a tool and, like any tool, its usefulness depends on what you're using it for and how expensive it is.

Bad debt

Bad debt is debt with a high interest rate used to buy things that don't generate income or appreciate. Credit cards, payday loans, buy-now-pay-later plans, high-APR personal loans, and car loans at punitive rates all fall in this bucket. The math is brutal: a 24% APR credit card balance roughly doubles every three years.

Put dollars on it and the picture sharpens. Carry $8,000 on a card at 24% APR and make only minimum payments, and you'll spend well over a decade paying it off while handing the issuer roughly $9,000 in interest — more than the original balance. The thing you bought is long gone; the payments outlive it by years. That's the defining feature of bad debt: the cost survives the purchase.

Good debt (or at least, not bad)

Debt used to buy something that makes you more money, or that carries a low enough rate that it's cheaper than the alternatives, can be fine. A mortgage at 3% that lets you buy a home in a rising market. A student loan for a degree that doubles your income. A 0% APR promotional period on a credit card used strategically and paid off before it expires.

The common thread in good debt is that the asset or income on the other side of the loan outruns the interest. A $30,000 loan at 6% that adds $40,000 a year to your earning power pays for itself many times over. The same $30,000 at 6% spent on a wedding or a truck you didn't need has no other side — it's just a rate attached to a memory. Good debt is rarer than lenders suggest, but it exists, and refusing it on principle can cost you real money too.

The middle — context-dependent

• Car loans: depends on the rate and whether the car is a need. 2% auto loan on a reliable used car? Fine. 9% auto loan on a depreciating luxury car? Bad.
• Student loans: depends on what you studied and what you do now. A $200k loan for a $50k career is a disaster. A $30k loan for a $120k career is a bargain.
• Mortgages: cheap debt on an appreciating asset is mostly good — but only if the house payment fits your life.

How to run the numbers on any debt

Before taking on any loan, answer three questions. First, what's the true APR including fees — not the monthly payment, the rate? A $2,000 'low payment' furniture plan can hide a 30% effective rate behind a friendly weekly number. Second, what will the thing you're buying be worth when the loan is done? A house probably holds or gains value; a car loses half; a vacation is worth zero the day you fly home. Third, does the purchase change your income? Education, tools, and reliable transportation to a better job can; almost nothing else does.

Common mistakes with the framework

• Calling debt 'good' because the purchase feels responsible. A degree with no career plan, a rental property with negative cash flow, or a bigger house 'as an investment' can all be bad debt in a respectable costume.
• Ignoring the payment's effect on your life. A mathematically fine mortgage that eats 45% of your take-home pay is a bad loan for you, whatever the rate.
• Keeping cheap debt while carrying expensive debt. Paying extra on a 3% mortgage while revolving a 24% card balance is burning money for the feeling of progress.
• Assuming you'll be the disciplined exception. 0% offers, deferred-interest plans, and 'I'll pay it off at bonus time' all price in your best self showing up. Underwrite your average self instead.

Good debt can still be too much debt

The framework has one more layer: even genuinely cheap, productive debt can sink you through sheer volume. A 6.5% mortgage is 'good debt' right up until the payment leaves nothing for retirement contributions, car repairs, or a job loss. Lenders will approve payments that consume 45% of your gross income; that approval is a statement about their risk, not your comfort. A useful personal ceiling: total debt payments under 36% of gross income, housing under 28%. Inside those lines, good debt behaves like a tool. Outside them, even a great interest rate becomes a monthly emergency.

Volume also interacts with time. Two 'good' loans taken in the same year — a mortgage and a car note, say — can each be defensible alone and jointly leave you with zero slack for a decade. Before adding any new debt, run the whole stack: every payment, every rate, every end date. The question isn't whether this loan is good. It's whether your life, with this loan added, still has room in it for something to go wrong.

The rule

When in doubt, assume it's bad debt. People who treat a 0% loan like free money usually pay 20% in the end. Debt is gravity — you feel it less while it's working in your favor.

And when you already hold both kinds, order matters: attack the highest rates first, protect the cheap fixed-rate debt last. A portfolio with a 6.5% mortgage and no card debt is healthy; the same mortgage plus $15,000 revolving at 24% is a slow leak. The label on the debt matters less than the interest actually leaving your account each month.