Cal. Civ. Code § 301

  § 301. Certificate of compliance or occupancy. 1. No multiple dwelling
shall be occupied in whole or in part until the issuance of a
certificate by the department that said dwelling conforms in all
respects to the requirements of this chapter, to the building code and
rules and to all other applicable law, except that no such certificate
shall be required in the case of:
  a. Any class B multiple dwelling existing on April eighteenth,
nineteen hundred twenty-nine, for which a certificate of occupancy was
not required before such date and in which no changes or alterations
have been made except in compliance with this chapter, and
  b. Any old-law tenement, or any class A multiple dwelling erected
after April twelfth, nineteen hundred one, which was occupied for two
years immediately before January first, nineteen hundred nine, and in
which no changes or alterations have been made except in compliance with
the tenement house law or this chapter, or wherein:
  (1) two or more apartments are combined creating larger residential
units, and
  (2) the total legal number of families within the building is being
decreased, and
  (3) the bulk of the buildings is not being increased
  These exceptions shall not be deemed to relieve any owner from the
obligation to make every alteration required in any old-law tenement or
other multiple dwelling in compliance with the applicable provisions of
this chapter.
  2. Except as above provided, no dwelling constructed as or altered or
converted into a multiple dwelling after April eighteenth, nineteen
hundred twenty-nine, shall be occupied in whole or in part until the
issuance of a certificate of compliance or occupancy.
  3. Such certificate shall be issued within ten days after written
application therefor if the dwelling shall be entitled thereto. The
department shall, on request of the owner or of his certified agent,
issue a certificate of compliance or occupancy for any existing multiple
dwelling not requiring such certificate, provided that, after an
inspection by the department, no violations are found against such
dwelling.
  4. The head of the department may, on the request of the owner or his
certified agent, issue a temporary certificate of compliance or
occupancy for a multiple dwelling or a section or a part thereof for a
period of ninety days or less, provided that such certificate shall bear
the endorsement that the dwelling has been inspected by the department
and complies with all the requirements of this chapter, and that such
temporary occupancy will not jeopardize life, health or property. Such
temporary certificate may be renewed at the discretion of the head of
the department for similar periods but shall not extend, together with
such renewals, beyond a total period of two years from the date of its
original issuance.
  5. A certificate, a record in the department, or a statement signed by
the head of the department that a certificate has been issued, may be
relied upon by every person who in good faith purchases a multiple
dwelling or who in good faith lends money upon the security of a
mortgage covering such a dwelling. Whenever any person has so relied
upon such a certificate, no claim that such dwelling had not, prior to
the issuance of such certificate, conformed in all respects to the
provisions of this chapter shall be made against such person or against
the interest of such person in a multiple dwelling to which such a
certificate applies or concerning which such a statement has been
issued.
  6. Notwithstanding any general or local law to the contrary, a
certificate issued for any multiple dwelling organized pursuant to the
provisions of article nine-B of the real property law, shall be deemed
issued for each dwelling unit contained within such multiple dwelling in
full compliance with the requirements of this section.
  7. a. Any certificate by the department authorizing occupancy of a
dwelling as a Class B hotel shall also authorize occupancy of units in
such dwelling for permanent residence purposes notwithstanding any
provision of this chapter or of any state law, local law, ordinance,
resolution or regulation that would otherwise prohibit such occupancy,
require a change or alteration to the dwelling, or require a new or
amended certificate, provided that: (1) such occupancy for permanent
residence purposes shall be subject to the approval of the local housing
agency in its discretion; (2) a portion of such dwelling shall be
located within a district that under the local zoning regulations or
ordinances permits residential uses or within four hundred feet of such
a district, and such dwelling shall not be located in an industrial
business zone established pursuant to chapter six-D of title twenty-two
of the administrative code of the city of New York; (3) in the case of a
property at which any hotel workers are represented by a collective
bargaining representative, prior to the proposed conversion of such
property to occupancy for permanent residence purposes, the collective
bargaining representative shall be notified in writing of the proposed
conversion, and the property owner shall certify prior to the local
housing agency approving such occupancy that the collective bargaining
representative has mutually agreed in a separate writing with the
property owner to undertake the specific conversion described in the
written notice; and (4) such dwelling shall meet the conditions in
paragraph b of this subdivision. Alterations to the configuration of any
such units shall be permitted and shall comply with any applicable
requirements of any state law, local law, ordinance, resolution or
regulation relating to Class B hotels. If occupancy for permanent
residence purposes is authorized under the provisions of this
subdivision within a district where the local zoning regulations or
ordinances would not otherwise permit such use, the residential tenants
shall be notified of the district's zoning.
  b. Occupancy of units in a dwelling shall not be authorized under the
provisions of paragraph a of this subdivision unless such units are (1)
financed by the state pursuant to and in compliance with the provisions
of article thirty-one of the private housing finance law; or (2)
purchased, acquired, or financed by a local housing agency, for the
purpose of creating supportive and/or affordable housing to be operated
by an appropriate nonprofit organization pursuant to a regulatory
agreement or contract with such local agency for low-income households
or people experiencing homelessness immediately prior to entering such
housing, where tenants shall earn no more than sixty percent of the area
median income and all units are rent stabilized and subject to permanent
affordability restrictions. For purposes of this paragraph, "appropriate
nonprofit organization", "affordable housing", "experiencing
homelessness", "rent stabilized", and "permanent affordability
restrictions" shall have the same meaning as defined in article
thirty-one of the private housing finance law.