I require this is I am paying for heat. 

If it's a baseboard heat (radiators) then you can install "zone valves" for a very reasonable price.

That attic must have had great ventilation; heat and dampness tends to break down the covering over the wire.

All units have HVAC (central air w/ heat pump) units less than 4 years old, upgrades galore including tile floors, recessed lighting, and all appliances included.

There are some features of this home that I would like to share to help me with the decision.This STR is only 6 years old, in very good shape, is year-round so has Heat/AC (which we do not) , a larger unit  (4bd / 4 bath & sleeps 12) & has been  booked each year with repeat vacationersThe property has not taken advantage of off season rentals, which happens in this area ( Oct - May) .I have included these #s conservatively in my NOI.I understand the formula for commercial investment property, NOI / cap rate.Can I use this same formula to evaluate a purchase price so I am not over paying for the property...

The heat in the summer gets to over 110° for several weeks (not fun for a mailman to be working in unfortunately)There is a climbing homeless population in our town and rates of crime are not the greatest, but also not the worst.

My property manager recommends:All Kool Heating and AirMike Nichols336 698 6820But I do not know him personally.

Is the building electric heat?

A high resistance short that doesn't trip circuit breakers is usually generating massive heat at the short point.

In addition, you need to account for other things such as vacancy, maintenance, and capital expenditures (like a new roof or heating system).