Identify the parties involved in the transaction. 2. A business purchase agreement marks the official start to the sale of a business.Read our blog to better understand each part of this important document. The easiest way to create a Business Purchase Agreement is to use a template that is customized to your state. Use a Business Bill of Sale to set out the terms for the sale of a business and transfer the ownership and all assets to the buyer. A business sale agreement is a legal document that describes and records the price and other details when a business owner sells the business. The deal memo or letter of intent will form the basis for the Purchase Agreement, which will incorporate these points into a formal contract. Any purchase of an existing business should be done with a written business purchase agreement.