Get the 7 day notice to quit form delivered to them as soon as possible. That is the first step in the process and basically gives them 7 days to pay up or get out. Bad thing is - if they do neither, you'll have to take them to court and wait it out, which you can't do until the 7-day notice is delivered to them. I went through this last year and made the mistake of being too lenient and the process took longer than what it should have. I don't care if they say they'll pay or not - if you've delivered the form, you have the ball rolling, which is the important thing.