California Code, Revenue and Taxation Code - RTC § 7281

The legislative body of any city or county may levy a tax on the privilege of renting a mobilehome, as defined in Section 18008 of the Health and Safety Code, which is located outside a mobilehome park for occupancy on a transient basis unless such occupancy is for any period of more than 30 days.  Such tax when levied by the legislative body of a county shall apply only to the unincorporated areas of the county.

This section does not authorize any city or county to levy a tax on the privilege of renting any mobilehome when the tenant is an employee of the owner or operator of the mobilehome.