Legal Question in Landlord & Tenant Law in California

After they pay rent. However, as to the landlord, if you need to do an eviction all occupants regardless of the durration of their residency should be made parties to the proceeding.

You should also try to see if the guest is going to claim they are a renter, especially if they are a guest of the tenant. If they are a guest they are not subject to the laws as renters, but if you do not include them in the eviction suit they might then claim they gave money for the rent to the other tenant you kicked out so they should have been included in the eviction case. If you lose the case, including them might have some negative effects. It is a gamble to some extent.