A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services. This car purchase agreement template is a standard agreement made completely customizable for your individual needs.A vehicle sales agreement is a lawful arrangement summarizing the terms and conditions of a vehicle sale between a customer and a seller. 2. Odometer Declaration. A Texas motor vehicle bill of sale is a legal document used to demonstrate that a motor vehicle has been sold. All terms used and not otherwise defined herein shall have the meaning set forth in the Purchase Agreement.