A long form agreement for the purchase and sale of commercial real property in Illinois. A commercial purchase agreement is a legal real estate contract that transfers commercial property ownership from a seller to a buyer.Forms are state specific because real estate laws vary significantly from state to state. An agreement to sell real estate, or a purchase agreement, is a legally enforceable document that specifies the terms of a real estate transaction. Assignment and Assumption Agreement; Vacant Land Addendum; Commercial and Investment Real Estate Purchase and Sale Agreement. Colliers is the leading diversified professional services and investment management company. Work with us to accelerate your success! Create, commit to, and manage your agreements all in one platform with Docusign IAM. Electronically sign for free. Typical limited partnerships are in real estate, oil and gas, and equipment leasing and family partnerships.