Quote from @Jennie Ballard: If you are having to redo the plumbing, I would investigate submetering the water to each unit.

Adam Schiff Under Criminal Investigation For Mortgage Fraudby Tyler DurdenSen.

When I investigated, someone else had gained access to it and created an ad campaign.

Investigate.

They are now officially under investigation by the FL Attorney General.

But if you look at "New York Attorney General Letitia James is facing allegations of mortgage fraud" and "California Senator Adam Schiff is under a federal criminal investigation for alleged mortgage fraud, specifically concerning claims about the primary residence status of two properties"You probably aren't as high profile as they are, but strange things are happening.

Give proper notice when due, and then don't renew the lease when it is up.Tenants, especially experienced ones like yours, will understand that if they have a judgment after an l/t court case, they may lose their voucher if the judgment is left unpaid.Just a note:  you can easily check public records through the Unified Judicial System to investigate if a potential tenant has been evicted or charged with crimes.  

Federal Bureau of Investigation (FBI): - https://www.fbi.gov/investigate/white-collar-crime6.

Are you under investigation or review by the SEC2.

Some additional thoughts:1) How well have you investigated the comparables that support the $900 rent?