Honest John's Car Dealership advertises his "understandable" financing plan on car purchases as follows. You pay 10% of the car's full price up front and 4% of the car's full price in 30 equal end-of-month payments For instance, if a car cost $15,000, the upfront payment (down payment)would be 10% * $15,000 = $1,500, and the equal monthly payments would be 4% * $15,000 = $600 a month for 30 months. It would work similarly for other car prices