“I own a car dealership in North Carolina. We have a customer that wanted a car we located at another dealership. I told the customer the dealership didn’t want the car and that he would have to pay for it in advance. He paid for the car, and we went and got the car, in good faith. After we went and got the car, the customer said he didn’t want it. Who owns the car?”
You had an agreement with the customer under which you would get the car from another dealership and give it to him in exchange for the purchase price. Generally speaking, you performed your part of the agreement and now the customer is bound to perform his part and let you keep the funds in exchange for the car.
That said, some states provide exceptions to the common law where the purchase of an automobile is concerned (such as providing a period of days in which a customer can change their mind), so you should consult an attorney in your state.