§ 291. Recording of conveyances. A conveyance of real property, within the state, on being duly acknowledged by the person executing the same, or proved as required by this chapter, and such acknowledgment or proof duly certified when required by this chapter, may be recorded in the office of the clerk of the county where such real property is situated, and such county clerk shall, upon the request of any party, on tender of the lawful fees therefor, record the same in his said office. Every such conveyance not so recorded is void as against any person who subsequently purchases or acquires by exchange or contracts to purchase or acquire by exchange, the same real property or any portion thereof, or acquires by assignment the rent to accrue therefrom as provided in section two hundred ninety-four-a of the real property law, in good faith and for a valuable consideration, from the same vendor or assignor, his distributees or devisees, and whose conveyance, contract or assignment is first duly recorded, and is void as against the lien upon the same real property or any portion thereof arising from payments made upon the execution of or pursuant to the terms of a contract with the same vendor, his distributees or devisees, if such contract is made in good faith and is first duly recorded. Notwithstanding the foregoing, any increase in the principal balance of a mortgage lien by virtue of the addition thereto of unpaid interest in accordance with the terms of the mortgage shall retain the priority of the original mortgage lien as so increased provided that any such mortgage instrument sets forth its terms of repayment.