(i) A signed Asset Purchase Agreement. A business sale agreement is a legal document that describes and records the price and other details when a business owner sells the business.Asset Purchase Agreement. An asset purchase agreement (APA) will outline the details of the sale. North Carolina business law attorney Donald R. Fuller will draft and review purchase and sale agreements to protect client interests. In an asset sale, the new owner purchases the business's physical assets. The seller retains all rights to the legal entity.