If forced air, new ductwork?

I have learned how to install P-traps, how to wire breaker boxes, and how to re-run ductwork. 

I just had a furnace put in a one bedroom, and that cost me around $2000 installed with all new duct work throughout, but it was a buddy who did it...

More efficient, can control temp in each room, no duct work in attic, etc...

But unless you can separate the heat, meters are useless.Heat: Have professional look at the duct work.

Ventilation systems: Furnaces and heaters will either need to be replaced or cleaned throughout all ductwork.

I see the point about the old components as an item to negotiate as part of the offer price instead of after the inspection especially since it still works (surprisingly since it's a gravity furnace from 1952), however I will have to replace it and it may or may not have asbestos and will be costly since the ductwork will need to be replaced as well.

@Patrick@Patrick Collins- new roof, hvac unit (vents and ductwork already there), refinish floors, carpet, paint, tile bathroom.

I created 2 additional bedrooms upstairs that was just open storage (I added framing, ductwork, electrical, closet, window) but no bath upstairs. 

I beg you.All new plumbing risers and lateralsAll new windows, doorsAll new furnaces, ductwork, everything related to heatingAll new electricalNew RoofI would strip everything to the studs, keep existing sub flooring if you can (you can lay 3/4" plywood and shim to level if they're off), and rebuild from there.