A Pennsylvania residential purchase agreement establishes a legal arrangement between a buyer and a seller in a real estate transaction. All components of the Property, except the Personalty and.A Pennsylvania purchase agreement creates a secured contract for a residential property transaction. Sellers and Buyer agree as follows: 1. Parties. A memorandum of purchase and sale agreement is a legal document that protects a buyer from being outbid after the seller accepts their offer. This is a Legally Binding Contract; If Not Understood, Seek Competent Legal Advice.