There are two factors to considering when budgeting for a new car. First, what’s your down payment? A down payment is cash that you pay up front for your car—usually 10 to 20 percent of the sticker price. The larger the down payment, the lower monthly costs will be. Second, what’s your monthly payment? You shouldn’t spend over 35 percent of your monthly income on a car. However, this figure might change depending on any existing debt.