Might be able to have ductwork cleaned and sanitized.It can be done.

My thoughts, hire a contractor to connect the ductwork to get HVAC linked with this room which SHOULD mean we get to add this portion (approx 250 sq ft).

I'm wondering what is the current average cost, and seeking recommendations/advice.Ty  Are you replacing just the units--no duct work, line set, etc? 

If you are going to install forced air you are going to have to install some duct work if there isn't an existing system in place.

Is your current duct work in place and in good condition?

To make a long story short, the final inspection, according to this inspector, revealed some major problems with the footings, floor joist, ac duct work, water heater, and he wanted me to replace a 4" cast iron sewer pipe out to the main(because he suspected it could go bad in the future) and no insulation under the flooring in the crawl space.

Collingswood is one of those 100 yr old towns where the houses all have 12 inch baseboard and wood floors, which run the heating bills up, and not all houses have central, or even the duct work for it.

The $5-6k prices included the air handler and maybe the ductwork as well.

Oftentimes the 2/1 and 3/1 houses don't even have the ductwork for central heat and air.

Adding AC might be one, but with mini-splits, it’s less enticing to add duct work.