Not really sure how much is involved with replacement as some items have seen say there may be asbestos in the duct work.   

See the Zillow link for the property below; interior is only 2,000 sq. ft not 2,556 (2,556 includes the garage)https://www.zillow.com/homedetails/600-N-13th-Ave-...Work for this house would include turning it into a 3/3 while leaving the existing 2 car garage, 3 brand new bathrooms, remove the wall separating the kitchen from family room, refinish and/or replace kitchen cabinets (countertops will be reused), replace all exterior doors and windows with new impact glass, new HVAC system with duct work, minor electrical (high hats, new fixtures, inspection repairs), paint, new casing/baseboard, and maybe new interior doors.I have also listed below my report from bigger pocket calculator on my return for the flip.

Property info:700 sq ft studio/junior one bedroom with one full bath (has a dedicated sleeping area with translucent panels to provide some privacy from rest of unit), has a balcony, stainless steel appliances, exposed duct work, washer/dryer in unitLocated in U Street Corridor of Washington, DCFinances:Paid $348K in Feb 2011, current market value around $460K ($465K from Redfin, $485K from Zillow)Mortgage balance of $249K; PITI + condo fee is $23K/year vs. $2,400/month or $28,800/year in rent.  

If not, could you put the furnaces in the attic and have to run minimal duct work (duct work is usually easy to run in an attic)? 

Replace old boiler system with new HVAC unit and put new ductwork. 7.

For example part of the home is on a slab so you may need to break concrete to access things like duct work, pipes, etc.Anyone have any more insight on these?

We will be replacing the ductwork, as well as the subfloor and carpeting in at least one bedroom due to prior pet damage.What was the outcome?

I’m assuming by cosmetic you mean that you are not ripping out walls so you have duct work where you add a condenser, decent electric, Sheetrock or plaster in good shape, plumbing you can keep.

Did you try cleaning out all the duct work?

Has internal ductwork driving their heat but not the AC.