A homeowner allowing someone to occupy a single room in their home should find it easier to remove the lodger than the typical tenant.
If a homeowner allows a single "lodger" access to their dwelling, the homeowner can remove the lodger without having to go through formal eviction proceedings.
In California under Civil Code § 1946.5, a "lodger" is defined as a person contracting with a homeowner for a room within a dwelling unit that is personally occupied by the homeowner.
(Civ. C. § 1946.5.)
In order to classify a person as a lodger, the homeowner must retain access to all areas of the dwelling unit and have overall control of the dwelling unit.
If it becomes necessary to have the lodger removed, the homeowner must give the lodger a written termination notice.
The homeowner must provide notice to the person that is at least as long as the days between rent payments, not to exceed 30 days. (Civ. C. §§ 1946, 1946.5.)
Once the notice period expires, the homeowner can then treat the lodger as a trespasser and have the lodger removed accordingly by law enforcement personnel. (Civ. C. § 1946.5; See Penal C. § 602.3.)
This CA attorney comments on lodgers in CA:
Similar commentary:
lodger's vs. tenant's rights (rent, lawyer, house) - San Diego - California (CA) - City-Data Forum
The official State of CA commentary:
http://www.hcd.ca.gov/manufactured-mobile-home/mobile-home-ombudsman/docs/Tenant-Landlord.pdf