A real estate purchase contract is a legally binding agreement between the buyer and the seller of a property. CONTRACT OF SALE – OFFICE, COMMERCIAL AND MULTI-FAMILY RESIDENTIAL. PREMISES.This form is made available to real estate professionals through an agreement with or purchase from the California Association of REALTORS®. A long form purchase and sale agreement for commercial real property located in California favoring the purchaser. Use a commercial real estate purchase agreement to secure transactions and protect your interests effectively.