I have a friend who is a sublandlord in California and he's on a month to month lease. He wants to move out because the house is in a terrible condition and the subletters are terrible roommates. How can he legally do this?
Then if they are just month-to-month he should give a "30 day notice to quit" or a notice not to renew at the next rent payment. If they have been living in the property for more than a year, he will have to give a 60 day "notice to quit". There are certain circumstances that allow shorter periods (like failure to pay rent, violating a lease, or drug dealing from the property).
The "notice to quit" does not need to state any reason, only that they need to be out by a certain calendar date. The landlord should get a copy of this, sending it by registered mail is best, but other methods like sending email with read receipt may work as well.