A new 2 ton heat pump system costs about 1,300 and HVAC contractors tend to charge the most money.

Since there is one heater and one meter, the heat and electric will all be in my name as the land lord.

I would pull the hot water heat and put in 3 separate systems.  

I have worked in the heating and cooling business for 8 years.

I know if I was a tenant I wouldn't want to pay a high bill for someone else.That would be like one person runs the A/C at 65 all the time and the other at 80 but each pay the same amount for a bill.The electrical draw being higher could be for one tenants operations but also for having older mechanical parts such as AC/Heating that are inefficient.You need to read your leases very carefully to see what tenants are responsible for.

The market is heating up again so lots of opportunities to buy.

Roofs have just been replaced and the boiler heating system was replaced three years ago.

I know the area already pretty hot is heating up even more.

The central heat and air has been updated, it has newer vinyl windows, a good roof, electric and plumbing (pex) have also been updated.  

New Roof SidingAC/Heat UnitsDriveway/SidewalkWater Heater