As used in this chapter, unless the context requires a different meaning: “Notice” means notice given in writing by either regular mail or hand delivery, with the sender retaining sufficient proof of having given such notice in the form of a certificate of service confirming such mailing or hand delivery prepared by the sender. “Option payment” means the amount paid by the purchaser in a residential executory real estate contract in exchange for the right to purchase the property that is the subject of such contract at a specific price within a specified time. “Purchaser” means a person who enters into a residential executory real estate contract. “Residential executory real estate contract” means an installment land contract, lease option contract, or rent-to-own contract by which a purchaser acquires any right or interest in real property other than a right of first refusal and occupies or intends to occupy the property as his primary residence. “Vendor” means the person who sells, or proposes to sell, real property under a residential executory real estate contract.