N.Y. Comp. Codes R. & Regs. tit. 9, § 2525.6 – Subletting; assignment.

(a) Housing accommodations subject to this Code rented by a tenant pursuant to an existing lease may be sublet in accordance with the provisions, and subject to the limitations, of section 226-b of the Real Property Law, provided that the additional provisions of this section are complied with and provided further that the tenant can establish that at all times he or she has maintained the housing accommodation as his or her primary residence and intends to occupy it as such at the expiration of the sublease.
(b) The rental charged to the subtenant by the tenant shall not exceed the legal regulated rent plus no more than a 10-percent surcharge payable to the tenant if the housing accommodation is sublet fully furnished. Where a tenant violates the provisions of this subdivision, the subtenant shall be entitled to treble damages.
(c) The tenant may not sublet a housing accommodation for more than a total of two years, including the term of the proposed sublease, out of the four-year period preceding the termination date of the proposed sublease. The term of proposed sublease may, if lawful under this section, extend beyond the term of the tenant's lease, and an owner may not refuse consent to a sublease solely because it extends beyond such term. A sublease which so extends shall be subject to the tenant's right to a renewal lease.
(d) The tenant, rather than the subtenant, retains:
1. (1) the right to a renewal lease, whether or not the term of the sublease extends beyond the term of the tenant's lease; and
2. (2) the rights and status of a tenant in occupancy with respect to conversion to condominium or cooperative ownership.
  (e)
3. (1) Upon the consent of the owner to a sublet, the legal regulated rent payable to the owner effective upon the date of subletting may be increased by the vacancy allowance, if any, provided in the rent guidelines board order in effect at the time of the commencement date of the lease, provided the lease is a renewal lease.
4. (2) Upon the consent of an owner to an assignment, regardless of whether or not the lease is a renewal lease, the legal regulated rent payable to the owner effective upon the date of such assignment may be increased by:
  1. (i) the increase provided for in section 2522.8 of this Title; and
  2. (ii) which may be further increased by the vacancy allowance, if any, provided in the rent guidelines board order in effect at the time of the commencement date of the lease. Such increases shall remain part of the legal regulated rent for any subsequent renewal lease. However, in the case of a subletting, upon termination of the sublease, the legal regulated rent shall revert to the legal regulated rent without the sublet vacancy allowance.
(f) An owner may terminate the tenancy of a tenant who sublets contrary to the terms of this section, or assigns without written consent of the owner, but no action or proceeding to terminate tenancy based upon the nonprimary residence of a tenant may be commenced prior to the expiration date of his or her lease.
(g) For housing accommodations which are first made subject to this Code solely by reason of article 7-C of the MDL, nothing herein shall be deemed to prevent or limit the rights of tenants to sell improvements pursuant to MDL section 286(6).