Moving Thermostat Options?

[Sam Amir]

Hey Everyone,

So I'm currently enrolled in the school of hardknocks and learning things along the way...we recently bought a 6 unit building that has the buildings thermostat inside one of the tenants units. The previous owner used to live in that unit and so it made sense, to put it there. While selling the building, he put a tenant in there. 

Obviously, this is not going to work since we pay heat, so I was going over possible solutions and would like to get an opinion on what others have done/would do:

1) Move thermostat outside of tenants unit in either the hallway or down by the furnace. (Most costly)

2) Put a lockbox on the thermostat. Cheapest option, but accessibility to change the temperature is limited since I have to come into the tenants unit, which I would like not to do

3) Replace thermostat with a smart thermostat. In the middle option in terms of price and very accessible as I can adjust temperature through the app on my phone.

Has anyone replaced their thermostats with a smart thermostat? If so, how's that going?

Appreciate any help. Thanks!