Simplisafe security system - a decent wireless system runs I think $300-500, plus $15-25/mo for monitoring.

For me being a licensed agent I can keep track and monitor them everyday and write lowball offers with ease.

If the building is only one meter it's going to be difficult to get tenants to be happy with paying for the neighbor who plays with the thermostat.There are many digital tools to monitor a range. 

For $400 you could use http://energycurb.com/ , which is an electricity only sub meter that monitors 18 separate circuits and also makes the information available online in real time.  

There should be some good locals that monitor that state forum.  

We also closesly monitor Perrysburg, Anthony Wayne and Springfield school districts for inventory. 

So we are making do.We too have installed a landlord thermostat to better monitor the duplex.

Just send me a text or email and I can send over a couple of options we have been monitoring. 

Supreme Court ruling - New Jersey Monitor

They will be the first to tell you if there are any issues.And lastly, have cameras on the exterior of the house so you can monitor it.