A business sale agreement is a legal document that describes and records the price and other details when a business owner sells the business. Purchase and Sale of Assets.A business purchase agreement is a legal document used to set the terms and conditions of a business sale between a buyer and a seller. A forward settlement and sale of foreign exchange adopts the principle of actual demand, which is valued with several prices in one day. The sale of a business is a complex process requiring a true team effort. Sell agreement is a written contract between two or more owners of a business, or among owners of the business and the entity.