9 NYCRR § 2104.5 — Occupancy by landlord or immediate family (State Rent & Eviction Regs., via Cornell LII)

(d) Where the
landlord purchased and thereby acquired title to the premises on or after May
1, 1950, or where the landlord acquired his rights in the housing
accommodations (other than in a structure or premises owned by a cooperative
corporation or association) through an enforceable contract of sale of the real
property which meets the minimum requirements of this subdivision, no
certificate shall be issued under subdivisions (a), (b) or (c) of this section
unless the landlord on or before the date of the filing of the application has
made a payment or payments totaling at least 20 percent of the purchase price
or the assessed valuation of the premises, whichever is greater; provided,
however, that where the Administrator finds that equivalent accommodations are
available for rent into which the tenant can move without substantial hardship
or loss, or that undue hardship would result to the landlord, a certificate may
be issued although less than 20 percent has been paid. This requirement shall
not apply where the landlord is a former member of the Armed Forces of the
United States of America who obtained a loan for use in purchasing housing
accommodations guaranteed in whole or part by the Administrator of Veterans
Affairs. The contract of sale of the real property referred to in this
subdivision shall:

(1) give the purchaser the
right of immediate possession and assign all of the rents and income from the
property to the purchaser;

(2) not
give the purchaser the right to cancel because of failure to secure occupancy
of the premises;