Get a comprehensive understanding of Illinois real estate purchase and sale agreements with our indepth overview and free template. You (or the purchaser or transferee) must complete Form CBS-1, Notice of Sale, Purchase, or Transfer of Business Assets.What is needed for a Contract for Deed? The agreement must be written. No oral agreements will be eligible in a court of law. A For Sale By Owner contract Illinois must include: 1. The Purchase Price, 2. Learn about real estate purchase agreements and review tips for agents to protect buyers with well-prepared real estate contracts and negotiations.