An Illinois residential purchase agreement is a legally binding contract between the buyer and seller of a residential property. Seller shall also furnish Purchaser with: (i) an Affidavit of Title in customary form; (ii) a Bill of.Sellers are required to complete a property disclosure statement in which they respond to questions about the material condition of their home. An Illinois purchase agreement is a standard contract for selling real estate from one party to another. An Offer to Purchase Real Estate sets out the terms of a proposed real estate deal. Create yours now with our free form. Utilize a Letter of Intent (LOI) to initiate negotiations for a sale, summarizing the terms of a forthcoming contract agreement. Read about the legal terms and disclosures you must add to an Illinois real estate purchase agreement. Learn what required information you must include. A For Sale By Owner contract Illinois must include: 1.