Its a subject near and dear to my heart right now with two young adults (one is an engineer the other is a computer programmer).

These questions might be best suited for web designers or programmers/SEO experts..com is and most likely will always be the best.  

Also both of separate thermostats, but only the downstairs has air-conditioning.

It isn't the thermostat too is it?

Is your thermostat on 90 and someone  else has it set for 68?  

The thermostat is located in one unit, who is instructed to leave the heat set at one temperature.  

Thermostats,  many of the baseboard heaters have the thermostats on them and you will find the tenants won't use them so hooking up a thermostat on the wall helps.

But as a property owner/landlord I can see the issue with ROI of the equipment and monthly monitoring.That said, I think the more you can use your security system to provide tenants more "home automation" features (i.e. controlling lights, thermostats, locks, etc.) from their smart phones, I think that is where you may be able to recognize some returns, especially in "A" and "B" class neighborhoods.Just my 2 cents.Lee

If it is there do you have any money in your budget for servicing it or changing the thermostat vents etc?

I'm not a programmer, so I'm not sure I understand your response fully.