Pretend that you don’t have a trade-in vehicle, at least for the moment. If you tell the salesperson that the car you drove there with will be your trade-in, they will ask you for the keys so they can figure out the value while you shop. This is bad because if you decide to go to another dealer, it will be hard for you to leave since they have your keys. This gives them the upper hand and will help them keep you in their dealership until they sell you a car. Tell them it’s your mom’s car.