If so, Carrier, Bryant, York, EMI, would likely have replacement parts more available than a foreign manufacturer like Daikin, LG, or Mitsubishi.  

Our house meter power consumption is down by as much as 70% depending on what other fixtures or appliances are drawing power.In these scenarios, particularly where outdoor halogen lighting was replaced, the migration to LED lights should pay for itself in 3 - 4 years.Ductless heat pumps can be wonderful - we are using the Mitsubishi Mr.

I'm looking into the option of installing Mitsubishi mini split units in each apartment

I was looking at Mitsubishi systems that seem to be reliable and easy to install as I would like to get rid of the window units.

Mitsubishi has a wired module adaptor that allows a standard wall mounted wireless thermostat to connect to it.

It’s a 2016 Mitsubishi Outlander with 97k miles on it, and I know that will work against me.

(Something like the Mitsubishi in wall units)Any feedback would be appreciated

For the two studio apartments upstairs though we did use Mitsubishi mini-splits and they are amazing. 

I live in New England near the ocean and have no issue with those temps ( not all makes / models will work)   fujitsu attained sole source certification in 2016 and mitsubishi was close I work with a company that installs as far north as Mainewhlle it is recommended to have a second heat source these newer units can stand alone. check with your local installer for specific models

And that was just the heat in the garage.I would look into using Mitsubishi minisplits with electric baseboard backup.