Sheam first thing you should do is get a post office box so she & your adult son no longer have access to mail you get because how you will be using the mail is going to change a bit to get her out and you really don't want her to be able to just grab the mail out of the box and destroy your proofs. SO if she has lived in your home for less than one year in CA you can write a 30 day notice and you don't have to make it complicated ( Date , her name , this is your notice that you must vacate address by ( date ) Your name and sign it with your new post office box as your address. AS to your son since love is so grand then if he has lived with you for more than one year its a 60 day notice ( these notices are still required even if someone doesn't have a written lease ( if you think he is so in love he will leave with her -follow her then maybe you want to give them each a 60 day notice. Make extra copies and send them via certified mail or confirmed mail delivery and staple your copies to your postal receipts and store them away from the house so your copys are safe from being destroyed. AS far as your concerns about a so called legal apartment If all you were doing was charging her to live with her boyfriend, your son in his bedroom space then I suggest you not worry about it since she / he are just roommates with you and not in a totally separate apartment ? Plan for filing with the courts if she /he wont leave. your filing would be based on that you gave proper notice to vacate and she /he refuse to move out, The court will verify that your notice was proper and if the judge agrees the notice was proper then they will be given x number of days to get out or face the possibility of county sheriffs deputies following a court order where they will be made to leave by hook or crook by the deputies in order to get them out and give your space back to you. ( your states landlord tenant links should be re checked incase they changes any thing about landlords giving proper notices to end month to month tenancies )