If it's as bad as you say, you may have to replace the a/c unit and possibly the air ducts, just something to think about.  

I do see you may want to do central air & heat...

The evaporator coil must be clean of any obstacle, this way the air will flow.

Once the house was lightly staged with furniture, we put air fresheners throughout the house and listed it on the market.

Also, what clauses outside "and/or assigns" should I make sure are absolutely in my purchase agreement & is there a way to make it air tight legally without paying an expensive fee for legal review?

Also it's hard to negotiate from a position of weakness and it sounds like your case is less than air tight.

All we did to the house was clean and paint, it already had a 4 or 5 year old gas furnace and central air.

They put a building and surrounding air rights under contract for $49M and wholesaled it to a developer for $59M.

This is based on daves comments on air about each of his 12 llc's being worth 5 million apiece.

(Cozy is free but very limited in its functionality and no customer support with the exception of via email)I know it probably doesn't do all that tenant fracker does but it does take the issues out of getting paid which was the biggest hassle in my opinion.