Brush up on building code requirements: in basements you're looking for egress windows that are 5.7 sq feet or more openable (3ft by 3ft casement style windows work best), and ceiling heights 6ft 8 inches or greater (as little as 6 ft 4 inches is ok under ductwork and beams though)3.

I'll be closing on a triplex soon and 2 of the 3 units share duct work (furnace/ac).

For some houses that are pet free they have new ductwork, never exposed to pet hair, etc. 

If  $1000, then I would consider split-units or central air if you can get the duct work to fit into your units. 

I was also able to raise the ceiling by 14” because I switched to exposed spiral ductwork.

Brush up on building code requirements: in basements you're looking for egress windows that are 5.7 sq feet or more openable (3ft by 3ft casement style windows work best), and ceiling heights 6ft 8 inches or greater (as little as 6 ft 4 inches is ok under ductwork and beams though)3.

Depends on if you will be doing duct work and switching out the existing units or just switching out the existing units?  

Lesson of the day: after getting a new AC tell your installer my story and tell them to double check the ductwork connections.

To "fix" the issue of room temp A/C company said would cost thousands per room to tear into the wall to check the ductwork.

Have you checked the duct work you may have a leak?