They've been paying for groceries during the pandemic the same way as prior to the pandemic - food stamps.  

Some things come to mind: The property manager should send you photos with time/date stamps on it as well as video.

Now, if you refi'd as a primary and moved out completely then that would be mortgage fraud.3)  Drawings:  Typically your local jurisdiction will require a stamp on those drawings.  

A subscription to white pages (about $20/month), an auto dialer (mojo is about $90/month), and enough stamps to send 100 letters to areas that fit your investors' criteria. 

Make sure whoever you use that you require time stamped photos. 

I'd also take down the address and go back an pull the tax records on the property to see if I could gleam any info on the tax records, like owners with different addresses etc, or owned forever and then do targeted live stamp "handwritten" letters.  

Typically nominal stamps are paid with the deed.

No one likes to write letters anymore or has stamps....so that can help resolve what is serious and what is bogus. 

Similarly with looking up at your floor joists and support beams to locate load bearing walls above them.its likely the permit process will require an engineers stamp on your submitted drawings for any alteration to structural components.  

I found this deal cold calling and gave him an as is offer with concessions being paid out by the seller minus doc stamps on the deed.