The key documents in a seller financing transaction include: (1) Purchase Agreement; (2) Promissory Note; and (3) Deed of Trust. Seller financing requires: An asset purchase agreement between the seller and buyer.Many Buyers will require that a sale be structured as an Asset Purchase in order to avoid responsibility for prior liabilities or expenses of the business. An owner financing a business for sale means the original owner will personally finance all or a portion of the purchase price. Seller financing: Under this contract, the seller consents to get paid in installments, frequently with interest.