Today i cant drive past an apartment building without trying to see the deal that lies within, i will pull off the highway if i spot a building i haven't seen before (drives my wife nuts) i keep a camera and a note pad in our vehicles.As @Joe Villeneuve alluded to above come up with a plan on what kind of investor you want to be, and work that plan tweaking it as you go and keep moving forward, everything else will start falling into place. 

At the same time it would be pretty simple to install security cameras. 

First upgrade security and have camera working or non working at every entrance and every corner of the building.

The only companies I see doing self showings in my market, are also installing cameras in every unit while it's vacant.

Security cameras are in place as well.I'd rather negotiate with him than do small claims but I will make sure there is a trail of emails either way.

But there is also a security camera facing the door.

I guess the best safeguard if you want to do it is cameras and electronic locks with codes you can change remotely.

If you must buy, install security cameras that you can access from the internet.

Concerns: Unit 1 is rented out to a couple who has security cameras everywhere.

It might be worth a plumber to send a camera down the main sewer to check the condition.