Easiest way is to have a programmable thermostat that allows you to set minimum and maximum limits.

My quarterly water/sewer bill is just south of $1200 on the 5 family, heat this month $250.It was built into the rent when I took over and after I implemented conservation/ regulated thermostats and insulation my profit jumped (one heat bill was almost $800, prior to sale).You are set up with separate meters- If you chose to split the bill I would consider whether you can institute cost saving measures first that may give you a profit.

If you use a Nest thermostat for a rental how do you hand off control to a new tenant and terminate control of the old one?

I respect the ethics and definitely agree that it will help to draw an ideal tenant base to you.I'm not sure what your HVAC, plumbing, electrical set up is like in your building, but there are plenty of energy efficient solutions for things like hot water, thermostats, etc.  

I also automate everything, doorlocks, thermostats, cleaning, bill pay etc. good luck

(3) Is it necessary to install a separate thermostat for the AC/heater in the basement?

I believe the thermostats are $50 off right now.

This allows you to add/delete door codes remotely and track people coming and going as it logs every time the door is locked/unlocked and by whom.Smart Thermostat.

Namely, thermostats that limit the temperature.

It turns out, the handy tenant replaced the thermostat incorrectly w/o our knowledge.