Unfortunately it turned out not really to be possible to sub-meter the gas, becauase there was not room to add 4 furnaces and separate ductwork for the units.  

Because the Thermostat is turned so low, a lot of condensation is forming on the ductwork inbetween the first floor ceiling and the second floor floor.  

All of the duct work is much easier working on a flat slab rather than a rough dirt surface.

Demo Total Bath and kitchen           Walls and ceilings           Windows, doors and trim         Floors where damaged         Rent dumpsters           Total labor 5580             Exterior Painting           Pressure wash house         Caulk where needed           Paint house           Total labor and estimated materials 4850           Foundation         Reinforce existing footings         Replace floor joists where needed and install new subfloors   Install new floor joists in addition to level with existing house   Total labor and estimated materials 8875           Plumbing           Replace pipes throughout       Run new pipes to accommodate new layout     Replace main water line         Total labor and materials       7500           Insulation             Install insulation in attic         Install insulation on walls       Total labor and materials 4580           Electrical           Update electrical throughout       Total labor and materials 7850           HVAC           Install a new HVAC system       Install new duct work       Total labor and materials       5890                                                                                             Interior work         Total Open up living room to dining room       Create 3 bedrooms and 3 baths         Install sheetrock on walls and ceilings       Mud, sand and prime walls and ceilings     Total labor and estimated materials     12785 Trim work           Install baseboards throughout         Install trim around windows and doors casing   Install new interior doors       Total labor and estimated materials     4850 Interior Painting Paint ceilings           Paint walls           Paint trim             Total labor and estimated materials 3580 Wood Floors Repair wood floors         Install new floors in addition       Sand and stain floors throughout     Total labor and materials       6750 Master Bath Build a concrete pam in shower         Install hardy boards on walls and floor       Install tile on floor and walls throughout       Install sink cabinets, toilet, and faucets       Install light fixtures and accessories, install glass shower door Total labor and estimated materials     7500 Guest bath         Install tub             Install hardy boards on walls and floor       Install tile on floor and walls         Install faucets, sink, and toilet         Install light fixtures and accessories     Total labor and estimated materials     5750                                                                                           Guest bath         Total Install tub             Install hardy boards on walls and floor       Install tile on floor and walls throughout       Install faucets, sink, and toilet         Install light fixtures and accessories     Total labor and estimated materials     5750 Kitchen           Install hardy boards on floor         Install tile on floor           Install cabinets           Install sink and faucet       Install door knobs         Install granite and backsplash       Total labor and estimated materials     7500 Roof Remove old shingles and repair plywood Install new shingles (25 year warranty).

Bathrooms, kitchens, flooring, paint, siding, probably HVAC, as well as possibly plumbing and electrical. the owner also mentioned that someone who gave her some estimates for repairs found mold in part of the duct work.  

The systems are a bit more expensive but the savings on duct work labor and materials make it a pretty good deal.

Looking for "reasonable and experienced" HVAC company to install full system (gas furnace, AC and ductwork) in King of Prussia, PA area and the greater Philly area.

I installed duct-work, insulation, doors, bathroom vanity, shower, toilet, also sanded drywall and painted.

I really can't imagine you'd need sprinklers, but fire doors, maybe fire partitions between units (which amounts to rated extra drywall, not sharing ductwork, etc.).

3 different furnaces , all new duct work  you are looking at big $$$$ .