N.Y. Real Prop. Acts. Law § 320

§ 320. Certain deeds deemed mortgages. A deed conveying real property,\nwhich, by any other written instrument, appears to be intended only as a\nsecurity in the nature of a mortgage, although an absolute conveyance in\nterms, must be considered a mortgage; and the person for whose benefit\nsuch deed is made, derives no advantage from the recording thereof,\nunless every writing, operating as a defeasance of the same, or\nexplanatory of its being desired to have the effect only of a mortgage,\nor conditional deed, is also recorded therewith, and at the same time.\n