Legal Question in Real Estate Law in California

Most rent control is on a community-by-community basis, so we'd have to know which Contra Costa County city or town; I haven't heard of any, but rent control probably exists somewhere in the county. Most rent-control ordinances limit increases in percentage terms, not number of times rent can be raised; one limit I have seen (Civil Code section 1947.7, a proposed standard that communities can adopt but isn't imposed) is 20% per year. I'd inquire locally; someone at City Hall can inform you.

There are statewide notice requirements, but you would have to provide more facts. If you are in a fixed term lease, such as a year long lease with a set rental rate, then the rent cannot be increased until the end of the term and there are notice requirements depending on the amount of the rent increase. If you are a month to month tenant, the rules are different.

You are also not clear on which city this may be in Contra Costa County, and there may or may not be a rent control ordinance that applies as pointed out by Mr. Whipple.