Banning tenant’s guest

[Jonathan Polack]

I own a duplex (new to the landlord thing). Both tenants in the upstairs and downstairs have been great and I want to keep them happy. The downstairs asked to do a sublease with an additional tenant to help afford it. I did not have a problem doing it as it is a three bedroom currently rented to a single person. Problem now is the upper tenants got a divorce. She has moved out, but now hangs out with the subleased tenant downstairs. It is causing an emotional nightmare for both the upper and lower tenants. And I am hearing that if things continue the tenants that have been great to me may just call it quits and move.

Question: do I have the right to tell a tenant their guest is not welcome on the premises? If so, are there only particular reasons that can be used? Do I have to CYA before making a statement? Is the fact that they are bothering other tenants and can cost me broken or renewed leases good enough?

Thanks in advance