It makes the unit a little less attractive but it keeps the tenants from doing stuff like opening windows because they get to hot, or leaving the thermostat at 76 ALL DAY. 

I get a 4 foot, 120 volt, 1kw unit with thermostat per room for well under $100/each. 

One thing you can do that helps, is make sure when you put in a new programmable thermostat that the owners/tenants understand how to program, and have the instructions :)

This is a DC low-voltage set-up - not unlike a door bell, thermostat, central vacuum switch, etc - 18 gauge (or 16 for the longer runs) should be sufficient unless you are worried about drop over 70ft (which should not be an issue).

We use a lock box and I have WiFi thermostats that I can control temperature when no one is there.If I moved further away I would just need to set up a cleaner and someone to maintain the yard and could still easily keep doing the property management.Key is to get a good support staff in your area.

Tip- install a spare thermostat sensor.  

I'm looking for a good landlord thermostat.

And I control that with wireless thermostats.

Home staging, furnishing, included beach toys/boards, smart locks/lights/thermostat are a worthy investment and will push it into the high margin zone.

Heat it is too expensive to separate so we include it and work on ways to decrease cost like insulation windows, and landlord thermostats.