A lot of tennats do not change air filters ever and that causes a major restriction on air flow.check condenser (outside coil) alot of the times they end up getting filled with leaves grass clippings etc.

Anyway, here's the quote my property manager got:3.0T Down Flow 80% gas Furnace 3.0T coil 410a coil 3.0 T 14.3 Seer CondenserNew thermostatSafety switchCondensation pump1 supply plenum2 Solid return boxes$7,315.00This comes with a 10 year warranty on equipment and 1 year labor.This seems way above what it needs to be. 

I would recommend having coils cleaned, refrigerant charged to spec, proper safeties installed (and working) such as high pressure switches and float switch.

You may not need a power roofing nailer to put shingles on a house. 

I would zone it with 2 systems with the handlers in the Attic and Basement  Still looking around $10-12k with condensers, coils, and sheet metal 

Just hire a tub refinisher they are usually $250-300Also I don't see how you can charge him for the dirty coil.

I nkow I could add an A-coil and condenser to the furnace for central air, but in this price range it doesn't really matter if they use wall ACs.I think I answer my question already, but what do you think?  

BUY quality SINGLE FAMILY homes SFH.that appreciate.4.Always do a home inspection using a certified home inspector ( with utilities turned on) and separately  hire an A.C. company to thoroughly inspect the state of the HVAC ( it might be blowing cold air today , which passes a home inspectors test) but the coils might be shot and the system riddled with leaks and crushed air handling tubes.

Central air is when they put a coil and condenser on the the forced air system so that the duct work is shared between the two. 

That means that in 10% of 50% of cases, we run into a situation where we didn't budget for a compressor replacement that we needed.  10% of 50% is 5% of our projects, and a compressor replacement is between $1000-1800 (depending on whether I need to replace the coil).