If you are a month-to-month tenant, and you are not living in a community with a rent control ordinance, then your rent can be increased on one rental period's notice. If you're in a rent control community, you will need to check the governing ordinance to see when rent may be increased and in what amount.
If you have a lease term (e.g., a one-year lease), the rent would normally be fixed by the lease for its entire term, and thus not subject to increase until the end of the lease term.

