Disclaimer: The materials provided below are informational and should not be relied upon as legal advice.
If you have a lease or rental agreement with your tenant, you should read it over carefully. The better drafted instruments will set an occupancy limit which will make this matter easier to deal with. Short of that, you probably cannot much object to the number of occupants unless they are causing some sort of nuisance. Be sure to consult your own attorney to protect your legal rights.
I agree with Attorney Mashal. What kind of tenancy do you have with this tenant? In a month-by-month agreement, landlords have more freedom to change rates, but they are still required to give a tenant at least 30 days’ written notice before the new rate takes effect. The rate on a fixed-term lease in California can only be increased by less than 10 percent if the tenant is given 30 days’ notice; a 60-day notice is required for any increase over 10 percent.
In a long term lease agreement, the the landlord cannot raise rent while the lease is in effect, unless the lease expressly allows rent increases. Also, the landlord cannot evict the tenant while the lease is in effect, except for reasons such as tenant damaging the property or failing to pay rent. To reiterate and explain further: if a tenant has a lease for more than 30 days, his/her rent cannot be increased during the term of the lease, unless the lease allows rent increases. However, in a periodic rental agreement, the landlord can increase rent, but the landlord must give you proper advance notice in writing. the written notice tells the tenant how much the increased rent is and when the increase goes into effect. California law guarantees tenants at least 30 days’ advance written notice of a rent increase if its a month-to-month (or shorter) periodic rental agreement. Under the law, the landlord must give the tenant at least 30 days’ advance notice if the rent increase is 10 percent (or less) of the rent charged at any time during the 12 months before the rent increase takes effect. The landlord must give the tenant at least 60 days’ advance notice if the rent increase is greater than 10 percent. So the increase in rent increase is governed by your lease agreement covenants and the CA law on notices. This link should help you a little bit: http://www.utsandiego.com/news/2013/May/27/tp-what-to-do-if-your-rent-increases/ ....Looks like San Diego only has just cause eviction protection only. http://docs.sandiego.gov/municode/MuniCodeChapter09/Ch09Art08Division07.pdf
Please consult with an attorney in San Diego for a second opinion, because each City/County has their own ordinance. BUT to my knowledge, I only see that San Diego has justice cause eviction protection ONLY. Also you should check out this link regarding sq. ft size of a room and how much to charge: http://www.dca.ca.gov/publications/landlordbook/catenant.pdf
*Disclaimer: This response does not create an attorney-client relationship between you and I. I am not your lawyer and I am not representing you in the underlying issue stated in your question. The response I have offered is not intended to be relied upon, you should seek out an attorney to assist in this matter. You may contact me directly at (415) 362-6765 ext.120; website: www.wc-advocateforjustice.com. (Attorney for Law Offices of William E. Weiss)