Rule Number 2 to follow when buying a car is never to talk about monthly payments until you have settled on the price of the car. If you tell the dealer that you are willing or can afford to pay a certain amount per month, you have given them the go-ahead to set the price of your car for you. The dealer will most likely offer you a monthly payment plan within (or slightly higher than) your stated parameters so that you will end up paying much more than you should be for the car in total.