My apologies @Chris Seveney, I failed to mention you in my previous reply but I see where you are no longer interested in the area. 

If they fail to allow access, they are charged a $100 trip charge fee.If their schedule doesn't allow them to be there, then I will open the home for the contractor.I try to respect the tenant's schedule, but I also expect them to respect mine and the contractor's.

The seller failed to pay bird dog.  

About 90% of the time they fail to meet HUD guidelines.HUD guidelines require that to qualify as an Emotional Support Animal, the prospective resident must have a letter from a licensed health professional, licensed in your state, in which the health professional acknowledges they have a relationship with the client that was more than just one session. 

Looking at a HUD home where the pressure test failed for the plumbing.

In which case you need to ask yourself, do you know all the issues with this property and why do you think you could succeed in turning this property around where this operator has failed.

If I can't find previous owner (building was forclosed - so seller was the bank), and all my efforts to find and talk with him have failed - why would the judge believe me over tenant?  

Increase in family size:A Borrower may be eligible for another house with an FHA-insured Mortgage if the Borrower provides satisfactory evidence that: • the Borrower has had an increase in legal dependents and the Property now fails to meet family needs; and • the Loan-to-Value (LTV) ratio on the current Principal Residence is equal to or less than 75% or is paid down to that amount, based on the outstanding Mortgage balance and a current residential appraisal.

If the tenant fails to provide the landlord with the forwarding or new address as required, the tenant shall not be entitled to damages or attorneys fees under division (C) of this section.”

Just take action each and every day, and fail forward.