NEC Article 300.8 states that no raceway can have elements of any other system besides electrical in it; no plumbing, no fuel gas, no ductwork.

@Billy SmithOur office is located in North Kansas City and we have a broad range for work performed that is best described as follows:Various styles of split system replacements and installation with in-house ductwork fabricationComplete roof sweep HVAC RTU replacement projects for school districts with in-house ductwork fabrication 5-105+ Tonnage RTU HVAC installation and replacement for larger commercial buildingsChiller, boiler, cooling tower and custom air handling unit installation and replacement for manufacturing and industrial facilitiesPlan and spec new construction HVAC projects with in-house ductwork fabricationVRF/Mini-Split plan and spec/replacement projectsIn-house ductwork fabricationMedical Marijuana Facility design build HVAC projectsDesign build projectsLarge Refrigeration(no ammonia, no grocery stores)Hope that helps!

Siding of residential home, duct work, electrical panels and dry wall. 

It looked good, and someone I trust checked it out for me - I'm out of state, but being there would not have changed anything, as I wouldn't have been able to identify duct work that's not to code, etc. by sight.

I'm not sure where you are (laws differ from place to place) or what's in your lease... but ripping up three year old destroyed carpet and cleaning pet urine out of the ductwork sounds like textbook usage of a security deposit to me.

It needs a new 5 ton unit downstairs and a new 3 ton unit upstairs, along with a fair amount of replacement and expanded flex ductwork.

You'll pay a little more for all the ductwork, but I believe it would be worth in the long term if you can make it happen. 

I could see tenants either not figuring out how to use them or losing them.. but NO duct work is very nice so mold is out of the game..  

So my question is spend $3k to get a boiler installed or spend $7k+ to get heat pump and ductwork installed?

I've researched the AC options a bit and there are 2 that won't require running duct work everywhere.