(Seller) agrees to sell the real estate and the property described above, if any, at the price and terms set forth herein, and to convey. A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price.How to fill out the Real Estate Sale Contract Illinois Form A? The Exclusive Right to Sell agreement is the most comprehensive and highest level of protection for the seller's brokerage company. Seller shall also furnish Purchaser with: (i) an Affidavit of Title in customary form; (ii) a Bill of. An Illinois residential purchase agreement is a legally binding contract between the buyer and seller of a residential property.