Find every fee trigger before you borrow.

True 0% APR means no interest accrues during the promotional period. Deferred interest accrues all along but is "waived" only if you pay the entire balance before the deadline. Miss it by a day and you owe interest retroactively from day one. Common in store financing and medical credit cards.

It lets the lender raise your interest rate based on a default with another creditor — even one totally unrelated to this account. Federal law banned this for credit cards in 2009 (CARD Act), but it still appears in some non-credit-card consumer loans.

They’re bad if you might want to pay off early or refinance. Mortgages with prepayment penalties typically charge 1–3% of the remaining balance, often only in the first 3–5 years. Always check the trigger window and the fee formula.

It means the lender can demand the entire remaining balance immediately if you trigger certain conditions — usually missed payments, but sometimes broader (selling collateral, declaring bankruptcy, or even a "material adverse change"). Acceleration clauses are normal but the triggers should be clearly defined.