There are two issues-the sublease and not paying rent.Do any of the neighbours have security cameras? 

Security cameras and signs showing that the property is actively monitored.

Set up cameras on your unit, even fake ones to discourage this person.

If the lease is signed by the owner of the property, locks, and security cameras belong to the owner and we (the management company ) just facilitate self-showings and then help the owner manage those showings and manage those tenants once the unit is rented.   1.

I just installed outdoor cameras.

I opted to buy a used camera and did it myself, it will pay off in a few homes, the value here is I can walk away from a home before even paying for inspection if there are a lot of hidden issues, or negotiate the price down (with photographic evidence).As an example, my most recent purchase, 1968 brick home had some cooling issues and I suspected attic and insulation, and what happened was they added blow-in insulation and covered suffit vents up. 

Replacing a fuse box with a breaker box (has to be licensed by the city), running a sewer snake through a cleanout hole (I don't want anyones feces on my body, not even my own), crawling under a house to fix plumbing (I'm claustrophobic and have panic attacks), dealing with intruders you catch on security cameras (I call the police and meet them there). 

This would include site prep, fence, basic electric, cameras and a simple office along with the buildings. 

They don't look at the cost as much.Don't kid yourself....also, their concern is Govt overreach/control and Nanny-statism.

Apart from getting a camera and inspecting the drains there’s no way to tell.