Getting rid of month to month tenant with troublesome boyfriend

[Eric Geurkink]

Closing on a duplex may 31. Currently both sides month to month. Rents will be raised and lower occupant has a cat (won’t be allowed), but also just learned she has a boyfriend (not on lease) who has also been a noise nuisance in neighborhood and punched out someone’s car window. I want to give her 30 days notice Right after closing, in the smoothest and safest  way possible. Will say due to rent increase and no pet policy, I am giving 30 days notice. I will plan to turn over June 30 and have new, well screened tenant July 1. 

2 questions (or anything else one would want to point out)

1. Other than discussing good references and treating them with respect and courtesy , how do I get them to pay June rent and not trash the place ?

2. What if they don’t leave June 30th? Can I get the police involved?

Thanks!