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 $$$$ . 

Add a $250 window, insulation, ductwork, vinyl tile, sheetrock, 1 light/fan. 

I've had it about 6 months, I've done all the work myself. remodeled the kitchen, knocked couple walls out, remodel the bathroom, turned it from a three bedroom to a two bedroom, put all new Plumbing and Electric in it, new Windows & Siding and ran all new duct work.

But if they are zoned correctly it shouldn't be too much, relatively speaking, to add two more systems or even check into newer minisplit heat pumps that work down to negative temps that don't require complicated new pipes/duct work through the walls. 

We look for asbestos floor tiles or asbestos in ductwork.