An apartment building in California with 16 or more units must have an on-site resident manager. Cal. Admin. Code tit. 25, § 42.
If your building is more than 4 units and less than 16 units, then a notice must be posted on the building informing the public of the phone number and address of the owner or owner’s agent (Management Company).
This is the text of the code:
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.