It used to have oil heat, the tank now is removed but plumbing and vent stack of bricks exist through the center of the house to the roof.  

If there is no central heating or water tank, you lose 6 months profit every time a furnace is replaced.

She's now our neighbor when we head of to Flagstaff to escape the heat.  

A consult might be 300 or so etc.You want to heat from the attorneys experience how these things tend to play out locally and options.No legal advice given. 

Radiant electric heat in floors in one building and gas furnaces in another.

A sonar scan will tell you more.We've done the repair for both water, heat, and steam.

(vapor barrier and foam insulation)* Ridge vent is totally clogged with dust, dirt or something that is preventing flow* There is a heat cord on the roof below where the furnace is located so I am sure the roof is hot in the winter and melts the snow which causes ice damn in the section.* vents and returns are in ceiling..so won't the heat come down and go right back up the return?

It needs foundation work, heat, electric updating.    

The units share a wall, heat/ac source, and address. 

If the house is 100 years old with wood heat and split shaker shingles, you need higher capital reserves.