A For Sale By Owner contract Arizona must include: 1. The Purchase Price, 2.First, go to AZMVDNow. Gov and activate your AZ MVD Now account. A master purchase agreement is a legally binding contract between buyer and seller, and typically relates to buying and selling goods rather than services. For private party sales — which are sales from one person to another — no bill of sale is necessary, but you might still want one for legal protection. You might write up a little agreement note and have both you and the seller sign it. But in the end, it's not worth the paper it's written on. How to properly fill out the Arizona Association of Realtors Resale Purchase Contract using Dotloop. Private sale I don't give down payments.