You can obtain the Residential Real Property Disclosure Report form from the Illinois General Assembly website. A For Sale By Owner contract Illinois must include: 1.The Purchase Price, 2. Illinois requires those selling FSBO to fill out and file many documents and forms. Several of these documents are legally binding agreements. An Illinois purchase agreement is a standard contract for selling real estate from one party to another. 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. BUYER agrees to purchase and SELLER agrees to sell the real property, and the improvements thereon, commonly known as: , in the County of. Without a Realtor to walk you through the process, you'll need a thorough understanding of what's legally required of you as a seller.