Model a reducing-balance asset loan with a deposit and optional balloon due at the end. See the monthly installment, full cash outlay and effective annual rate.
The deposit reduces the amount borrowed immediately. The balloon is still owed at maturity, so its discounted present value is removed before calculating the equal monthly installments.
Check whether the written quote uses nominal or effective interest, advance or arrears payments, variable rates, compulsory insurance, documentation fees, taxes, tracking charges and ownership-transfer conditions.