An Illinois residential purchase agreement is a legally binding contract between the buyer and seller of a residential property. The acceptance must be absolute, unconditional, and identical with the terms of the offer.Seller shall also furnish Purchaser with: (i) an Affidavit of Title in customary form; (ii) a Bill of. The answer lies in four critical ingredients: an offer, acceptance, consideration, and mutual intent to establish a legal commitment. Stepbystep guide on how to write contracts for leases, business partnerships, and employment contracts. ACCEPTANCE DATE: ("Acceptance Date"). SELLER'S INFORMATION: Seller's Signature: Seller's Name (print):.