California Code, Health and Safety Code - HSC § 1566.3

(a) Whether or not unrelated persons are living together, a residential facility that serves six or fewer persons shall be considered a residential use of property for the purposes of this article.  In addition, the residents and operators of such a facility shall be considered a family for the purposes of any law or zoning ordinance that relates to the residential use of property pursuant to this article.

(b) For the purpose of all local ordinances, a residential facility that serves six or fewer persons shall not be included within the definition of a boarding house, rooming house, institution or home for the care of minors, the aged, or persons with mental health disorders, foster care home, guest home, rest home, community residence, or other similar term that implies that the residential facility is a business run for profit or differs in any other way from a family dwelling.

(c) This section shall not be construed to prohibit a city, county, or other local public entity from placing restrictions on building heights, setback, lot dimensions, or placement of signs of a residential facility that serves six or fewer persons as long as those restrictions are identical to those applied to other family dwellings of the same type in the same zone.

(d) This section shall not be construed to prohibit the application to a residential care facility of any local ordinance that deals with health and safety, building standards, environmental impact standards, or any other matter within the jurisdiction of a local public entity if the ordinance does not distinguish residential care facilities that serve six or fewer persons from other family dwellings of the same type in the same zone and if the ordinance does not distinguish residents of the residential care facilities from persons who reside in other family dwellings of the same type in the same zone.  Nothing in this section shall be construed to limit the ability of a local public entity to fully enforce a local ordinance, including, but not limited to, the imposition of fines and other penalties associated with violations of local ordinances covered by this section.

(e) No conditional use permit, zoning variance, or other zoning clearance shall be required of a residential facility that serves six or fewer persons that is not required of a family dwelling of the same type in the same zone.

(f) Use of a family dwelling for purposes of a residential facility serving six or fewer persons shall not constitute a change of occupancy for purposes of Part 1. 5   1 (commencing with Section 17910) of Division 13 or local building codes.  However, nothing in this section is intended to supersede Section 13143 or 13143.6, to the extent such sections are applicable to residential facilities providing care for six or fewer residents.

(g) For the purposes of this section, “family dwelling,” includes, but is not limited to, single-family dwellings, units in multifamily dwellings, including units in duplexes and units in apartment dwellings, mobilehomes, including mobilehomes located in mobilehome parks, units in cooperatives, units in condominiums, units in townhouses, and units in planned unit developments.