N.Y. Comp. Codes R. & Regs. tit. 20 § 641.10
Tax Law, § 253-b
Credit line mortgage means any mortgage means any mortgage or deed of trust, other than a mortgage or deed of trust made pursuant to a building loan contract as defined in subdivision 13 of section 2 of the Lien Law, which states that it secures indebtedness under a note, credit agreement or other financing agreement that reflects the fact that the parties reasonably contemplate entering into a series of advances, or advances, payments and readvances, and that limits the aggregate amount at any time outstanding to a maximum amount specified in such mortgage or deed of trust. Provided, however, credit line mortgage shall not include a reverse mortgage created pursuant to section 280 or 280-a of the Real Property Law.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 641.10