My question involves landlord-tenant law in the State of: CA
So I have a month to month 3 bedroom lease under my name ONLY and that is how my landlord wants it. I have tried to add another person but he doesn't want anyone else on it but me. I have been leasing for 3 years.
There is a roommate who has been living with me for only four months. In the second month (this was in September) he had a friend stay over. I don't mind if a friend stays over because they got a little too drunk and can't drive but this guy was staying over every day. At first he was appearing once or twice a week then all of a sudden every morning when I leave for work I would see him sleeping in the living room. I texted my roommate what was going on and if his friend was staying at our place and if it was temporary. All he texted me back was "temp". Now he never introduced me to his friend and did not even ask if it was okay. It was a mess. He stayed much longer and I mentioned that he must pay for the time he's been staying at my place and be out. Then I hear from my OTHER roommate (who is no longer my roommate now) that the stranger was actually staying for a couple of months until he gets his VA check and thought I knew about it already, I was PISSED! I told him that we cannot have friends stay over like that again and he agreed. Didn't say sorry, nor did his friend thank me for not kicking him out right away. I think its fair that my renters should let me know and come to me and ask if its okay to have someone stay temporarily. I was totally out of the loop.
Forward to this month. I feel that he is doing it again but with my previous roommate (the one who told me that the stranger was staying until the VA checks come in). They are both good friends btw. The previous roommate moved out about a month ago and he messaged me a few days ago to ask if I had a room available, and I said no as I am having a family member of mine move in. Just yesterday morning I see my previous roommate and my other roommate outside in the backyard talking, I didn't think anything of it. Then I saw his car parked in front of the driveway with all his belongings in it. And right then and there I had a bad feeling but did not want to assume anything yet. That same day I come back from work and his car was still there but I didn't see him around the house unless he was in my roommates bedroom but I didn't hear anyone talking, nothing. I checked in the garage and living room to make sure he didn't place any of his belongings in there. But there was nothing. I have not said anything yet because it has been only ONE day.
I just want to ask for some advice on what to do if he is letting our old roommate stay without letting me know and if a 30-day notice of eviction will be proper for this kind of incident. There are other small incidents that has happened but this one is my biggest pet peeve. Him not communicating to me about whats going on is disrespectful.

