He may also insert charges you didn't request, and don't need, like extended warranties, rustproofing, and expensive credit insurance. It is illegal for a dealer to make you buy credit insurance or anything you did not request. By the way, the dealer will also be inflating the price of the extended warranty, which will overlap the manufacturer's warranty. Then they take the contract with them, not giving you your copy. Consumers trust them, and don't read terms and numbers.
Most consumers focus on the monthly payment.
Tell a dealer what you can pay, they will soak you for that amount, and more. Shop instead for the lowest APR, and reject unwanted extras. Don't let yourself be blinded by a shiny new car. Don't bring the kids when you shop for cars. The salesman will sell the kids, and you will have kids pressuring you to sign and go home.