This is in RI so letting the heat out is not just a big cost but a risk.

i do not however use it for heat mine is an AC only unit I believe not a heat pump unit.If you're whole unit is relying on one mini split for ac and heat that surprises me just given if you shut a bedroom door you'd not have heat from the split that I assume is in the living room. 

The unit shares the same heating and cooling as my own house.

Without electric you can not heat the unit.

hi all i am a new landlord and got my first rental property. tenants moved in in September and October. the first month was fine but when December hit it got extremely cold and the heating is electric. due to poor insulation in the home that we did not know about the heat has to be turned very high up to keep the home warm, however since everything is electric it is causing the electric bill to be $800. the utilities are the tenants responsibility. however because of this one of the tenants has been extremely non compliant with paying rent.

Where trust is low, though, things are slower or more expensive or both.- Understand that you can have never more than 2/3 of the following:  Fast, Good, and Cheap.  

We have a single HVAC system that heats/cools the entire home.

The lease language requires the interior of the building to heat to 70 degrees.

Not sure how they could block a sale but I imagine they told him the central heating unit for the whole complex would soon need replacement so a special assessment would be upcoming.  

Windows would be my next check-point (less than R1) and then wall insulation: I would not be surprised if they have no insulation inside, but you can do blow-in, which only requires a small hole.A home looses heat in two ways: heat conduction (which you can slow down with insulation) and drafts, which in old houses is usually the biggest culprit.