In a For Sale By Owner, the seller's agent is typically the person who draws up a real estate purchase agreement. A Texas residential purchase agreement outlines the terms and conditions of an offer to purchase real estate.1.01 Agreement of Purchase and Sale. Selling your Texas home without a realtor? You need to fill out the "AS IS" Residential Contract for Sale and Purchase to sell your house as is in San Antonio. Buyers may ask for the offer to be contingent on other factors, such as the sale of their existing home or their ability to obtain financing. This FSBO paperwork is needed as soon as you accept an offer, so it's useful to have a purchase agreement onhand that you can fill out quickly. Our San Antonio residential real estate lawyer assists sellers with purchase contracts and owner financing transactions. This FSBO paperwork is needed as soon as you accept an offer, so it's useful to have a purchase agreement onhand that you can fill out quickly. PURCHASE AND SALE AGREEMENT (The Parke San Antonio,Texas) from CIM INCOME NAV, INC.