You may want to check your local housing authority or commission for the exact guidelines that govern your area.Hope this helps!

See if you can get their authorization to go over there (you may not even need it but it's good to call and ask), give the shady characters a firm deadline to get out, and lock down the place with changed locks and an alarm system when the deadline passes.

Will the local authority make you raise an entire house? 

In my area, law students and housing authorities send "actors" out to walk properties and fill out applications in order to see who violates these laws and they file hefty fines regularly.The benefit of defining your criteria is that it makes it really easy to decide who you rent to, no more comparing applicants. 

A fine has to be levied by those with the authority to do so!

I have a seller who has agreed to sell property at a discount, however he has to turn self in to authorities because of domestic violence, I believe with in 20days to do so.

Or does it even matter, if the end result is the same --- having the authority to terminate a tenancy?

Have you verified the tax authority did Not notify them of the sale?  

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The property manager is your agent and should be authorized to act on your behalf.