California Code, Business and Professions Code - BPC § 7360

No person having charge of a mobile unit, whether as an owner or an employee, shall permit any room, or part thereof, in which any occupation regulated under this chapter is conducted or practiced, to be used for residential purposes or for any other purpose that would tend to make the unit unsanitary, unhealthy, or unsafe, or endanger the health and safety of the consuming public.

This section shall not apply when the mobile unit is used for purposes other than the practice of any occupation regulated under this chapter outside of the designated geographical boundaries for which it is licensed.