N.Y. Pers. Prop. Law § 314
No retail instalment contract, or any other agreement executed in connection therewith, shall provide for the creation of a security interest in any personal or real property, other than the motor vehicle which is the subject matter of the retail instalment sale (or accessories therefor or special or auxiliary equipment used in connection therewith), to secure the payment of the time sale price under such contract or any part thereof, provided, however, that the prohibition of this section shall not be applicable to the taking of a mortgage or other security interest upon or in connection with real property to secure the payment of the time sale price of a retail installment sale, if the subject matter of the retail installment sale is a mobile home or trailer which is to be annexed to or situated on such real property. Any such prohibited provision shall be void but shall not otherwise affect the validity of such contract.
N.Y. Pers. Prop. Law § 314