How to evict a tenant?

The first step to evict a tenant is to serve the proper notice, a 5-day for unpaid rent.  It's far easier to evict for failure to pay rent then other breaches of the lease (which are harder to prove), but possible as well (it requires a different notice, however).

It's certainly in your interest not to wait.  Bad situations almost never improve on their own.

I'd recommend that you have a lawyer help you evict these people.  There's a very detailed process, and it has to be followed exactly;  if you make a mistake, you have to go all the way back and start over from the very beginning.  Unless you know how to do this yourself, it will almost certainly be quicker, and probably less expensive overall, if you do get an attorney.

It sounds to me like you have the kind of bottom-feeding tenants who have run this sort of game many times before, and know all the details of the eviction laws and will take shameless advantage, to delay the inevitable and run up as much of an unpaid-rent bill as they can manage.  Don't wait to get the process started.