I'm new to car financing. What got me confused is that my bank wants purchase agreement or bill of sale before sending out a check to the dealer.A confusing and convoluted document that outlines the selling price, fees, taxes, your trade in, and more. You can prepare an Agreement for a Joint Purchase using the form included here. Simply fill in the details of your joint purchase. By filling out this form inquiry, you are allowing Kings auto group to contact you to proceed with a credit application. Yes, a purchase agreement is a valid and binding contract in NY IF the dodge dealership signed it. If they signed it, then they are held to its terms. Purchasing a vehicle is a big financial commitment! That said, it is important to know the ins and outs of your purchase contract.