Cal. Civ. Code § 10-A

  § 10-a. Right to sublease. Units subject to this law may be sublet
pursuant to section two hundred twenty-six-b of the real property law
provided that (a) the rental charged to the subtenant does not exceed
the legal regulated rent plus a ten percent surcharge payable to the
tenant if the unit sublet was furnished with the tenant's furniture; (b)
the tenant can establish that at all times he has maintained the unit as
his primary residence and intends to occupy it as such at the expiration
of the sublease; (c) an owner may terminate the tenancy of a tenant who
sublets or assigns contrary to the terms of this section but no action
or proceeding based on the non-primary residence of a tenant may be
commenced prior to the expiration date of his lease; (d) where an
apartment is sublet the prime tenant shall retain the right to a renewal
lease and the rights and status of a tenant in occupancy as they relate
to conversion to condominium or cooperative ownership; (e) where a
tenant violates the provisions of subdivision (a) of this section the
subtenant shall be entitled to damages of three times the overcharge and
may also be awarded attorneys fees and interest from the date of the
overcharge at the rate of interest payable on a judgment pursuant to
section five thousand four of the civil practice law and rules; (f) the
tenant may not sublet the unit 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 provisions
of this subdivision (f) shall only apply to subleases commencing on and
after July first, nineteen hundred eighty-three; (g) for the purposes of
this section only, the term of the proposed sublease may extend beyond
the term of the tenant's lease. In such event, such sublease shall be
subject to the tenant's right to a renewal lease. The subtenant shall
have no right to a renewal lease. It shall be unreasonable for an owner
to refuse to consent to a sublease solely because such sublease extends
beyond the tenant's lease; and (h) notwithstanding the provisions of
section two hundred twenty-six-b of the real property law, a
not-for-profit hospital shall have the right to sublet any housing
accommodation leased by it to its affiliated personnel without requiring
the landlord's consent to any such sublease and without being bound by
the provisions of subdivisions (b), (c) and (f) of this section.
Commencing with the effective date of this subdivision, whenever a
not-for-profit hospital executes a renewal lease for a housing
accommodation, the legal regulated rent shall be increased by a sum
equal to fifteen percent of the previous lease rental for such housing
accommodation, hereinafter referred to as a vacancy surcharge, unless
the landlord shall have received within the seven year period prior to
the commencement date of such renewal lease any vacancy increases or
vacancy surcharges allocable to the said housing accommodation. In the
event the landlord shall have received any such vacancy increases or
vacancy surcharges during such seven year period, the vacancy surcharge
shall be reduced by the amount received by any such vacancy increase or
vacancy surcharges.