It'll depend on how much payment you can afford. Work up a budget for other living expenses (rent, food, other loan payments, insurance, etc.). See how much you have left for a car payment. From there, look up how much car you can get with that payment. Don't get a loan over four years long (You'll pay back the loan quick enough to cover the depreciation). From there you will see how much down payment you'll need. As an estimate, if you can afford a $600 payment (7% on the loan) for 48 months, you'll have to put a $5000 down payment for a $30,000 car.