One thing we just discovered that cut down our expenses big time was installing NEST thermostats in both units since often times people forget to turn them back up when they leave and we can control and program them remotely. 

We built ours from a WP theme and we're not programmers so this is what we got.

It taught me a few troubleshooting tips (I already knew how to clean coils and make sure drain lines were clean).Because of this I saved myself several service calls that would have involved a high priced tech replacing; thermostats, exhaust fans and relays.

If this is a boiler system, you can install control valves and thermostats for each unit so they control their own heat.

The heating system is not zoned, but there is evidence (one for each unit) that it was once zoned in each of the 4 units as there are 4 separate pipes and old thermostats in the units that are inaccessible.

While I don't know everything about my HVAC system, I do know what the thermostat does, thankyouverymuch.Basically, the main issue that we face as women in an industry that is dominated by men is that we are very frequently pushed aside, particularly if we have a male partner. 

For the record, I am a computer programmer and I know some of the technology out there isn't worth the money people are paying for it. 

I have read here the multiple posts from the landlord concerned about tenant setting thermostat to the extreme causing excessive HVAC wear and tear. 

@Alex ReinsmaI use a ring door bell, Schlage encode for door codes (I can set a new code each guests, cleaners, handyman, etc), Wi-Fi thermostat, etc.  

They are plagued with issues.Same with nest thermostats.