I am installing HVAC into all 4 and the quotes I got for all units together was $18,500 - 20,000 ( or about $5000/unit including units and ductwork for 1300-1400 sf each)   They are running all of the ductwork through the rafters upstairs and in the basement apartments - I assume they will install in the ceiling somehow - They will not have to do anything to the slab (I know because I just spent a ton to replace the sewer line and put water, plumbing, and electric for the islands into the slab.) 

I've had to replace the water heater and some repairs to ductwork costing about $2300 so far.Would I work with them again? 

I am working on a property where I had to redo the duct work for a permit we had pulled...it was cheaper to pull the gas pack out (you can sell it for good money probably) and install baseboard heating.

Looking for someone to review HVAC systems in a multi-family property - specifically duct work design.  

I had a 2/1 , 934 square feet, and had a whole new system including duct work replaced for 3k but that was back in 2009. 

Not sure about HVAC but I added duct work and Boone county inspector was OK with it.

It would cost too much to do what he needs to do to get Power of Attorney or Guardianship and even then he is not guaranteed to be able to refinance so he can put in new HVAC duct work. 

In Austin people were mentioning pricing similar to what you listed and they were not sure it was a complete system.And this excluded finishes.That being said, if you are adding a complete system, make sure you locate vents and ductwork.  

But you are paying for the convenience of easy duct work. 

Here in South, you pretty much need central AC anyway these days, so once the ductwork is there, switching to central heat is a no brainer.Edit:  just noticed that you ARE in NC - I would replace them then, unless you are in a D area where window AC units are feasible