Section 420 - Guaranties to sellers of liabilities of buyers under retail instalment contracts(a) No guaranty given to the seller or to the seller and the seller's assignee of the liabilities of a buyer under a retail instalment contract shall be valid unless the guaranty is incorporated in or endorsed on the contract or identifies the contract and specifies the time balance thereof. A copy of the guaranty and the contract to which it relates shall be given or mailed to the guarantor upon or immediately after the execution and delivery of the guaranty by the guarantor. As used in this section, "retail instalment contract" and "contract" include a retail instalment obligation and a retail instalment contract as defined in the motor vehicle retail instalment sales act, constituting article nine of this chapter. This section does not apply to a guaranty made by a seller or a holder of a retail instalment contract.(b) No guaranty given to the seller or to the seller and the seller's assignee of the liabilities of a buyer under a retail instalment contract shall relate to any future retail instalment contracts.N.Y. Pers. Prop. Law § 420