Both the seller and buyer must draft this contract with information regarding the land's legal descriptors as well as the agreed-upon purchase price. An Illinois purchase agreement is a standard contract for selling real estate from one party to another.Address. City. State. Zip. County. Permanent Index Number(s) of Real Estate: ______-______-______-______. The Real Estate is vacant and unimproved. Get a comprehensive understanding of Illinois real estate purchase and sale agreements with our indepth overview and free template. Purchase and Sale Agreement. A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price. Add the names, contact details, and addresses of the required parties.