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Was there a written lease in effect when he bought your building?
As a month to month tenant in California the tenancy can be modified or terminated by the landlord upon 60 days notice to you.
So, unless he has given the required notice you do not have to begin the increased rent.
As I said, if the rent is increased by 10% or more he must give 60 days notice.
Less than 10% only requires 30 days notice.
You can refuse to pay the additional rent, terminate the tenancy and move out.
Otherwise, the landlord is generally allowed to charge whatever the market will bear in rent.
The only limitation is that the landlord can not increase the rent due to your race, religion, ethnicity, etc. That violates federal law.
There is no legal requirement of a written lease to have a valid tenancy.
Did you have further questions? I am happy to continue if you do.
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