Find out what documents you will need to provide proof of sale and ownership if you are buying, selling, or gifting a vehicle. You can prepare an Agreement for a Joint Purchase using the form included here.Simply fill in the details of your joint purchase. Watch this before you finance your next car (former dealer explains how to read a purchase contract) A purchase agreement is a type of contract that outlines terms and conditions related to the sale of goods. 1 If you're financing your purchase ; 3 The actual vehicle purchase agreement ; 4 Buyer's trade in certification ; 5 Warranty disclaimer and documentary fee notice. You'll need to sign the car purchase agreement (or dealer bill of sale), the title, an odometer statement, and sometimes a damage disclosure statement. If you're leasing a vehicle, most finance companies will include a buyout option as part of your lease agreement.