This form is made available to real estate professionals through an agreement with or purchase from the California Association of REALTORS®. A unique application of customizable commercial real estate contract templates, including Purchase and Sale, Lease, and Listing agreements.The heart of this journey lies in the Commercial Real. Estate Purchase Agreement, a legally binding document outlining the terms of the transaction between. The purchase and sale agreement (the "PSA") is the central document for the sale of commercial real property and one of the most important.