Can I use a trade in if I am looking to buy used cars? I know that dealerships will allow trade-ins if you are buying a new vehicle but I do not know if it works the same for used cars. Also, I have heard that you only want to make one transaction at the dealership. If you buy a car there, do not plan on financing or trading in. Should I try to sell my car first before I go to the dealership? That way, I guess I would not have to worry about if the dealership will take my trade-in or not.