When is an owner required to have an on-site manager for residential income property in California?

Here is what the California Code of Regulations Title 25, Section 42 of the California State Housing Law says on the topic:

§ 42. Caretaker (25 CCR § 42)

A manager, janitor, housekeeper, or other responsible person shall reside upon the premises and shall have charge of every apartment house in which there are 16 or more apartments, and of every hotel in which there are 12 or more guest rooms, in the event that the owner of an apartment house or hotel does not reside upon said premises. Only one caretaker would be required for all structures under one ownership and on one contiguous parcel of land. If the owner does not reside upon the premises of any apartment house in which there are more than four but less than 16 apartments, a notice stating the owner's name and address, or the name and address of the owner's agent in charge of the apartment house, shall be posted in a conspicuous place on the premises.