I’m in the process of buying another property and once it closes we’ll have to immediately install new smoke detectors and carbon monoxide detectors which he’ll have to take time from the apartment project to coordinate with the electrician on.

You are not a lie detector and you need to stop trying to figure out who is worthy and who is not.

Yep- motion sensor cameras are pretty cheap and easy to install nowadays.

Radon detector pretty pricey, infa-red camera, are you able to check electrical circuits? 

One good idea is to buy the $10 leak alert detectors that will scream like a fire alarm when they are in contact with water.

In WA It also means carbon monoxide and smoke detectors and water heaters are strapped. 

The first thing I do when I buy a property is update the CO detectors and the smoke detectors.

Our lender okayed us getting another 5+ unit property and we were going through the motions of getting the mortgage.

It would bode well for you to dig deeply into this before putting any real wheels in motion, as you'll be dealing with OPM and have a high level of responsibility and (therefore) risk.The book by Matt and Liz Faircloth on Raising Private Capital would be a prudent read. 

And of course working smoke alarms (and if gas, carbon monoxide detectors).