For a small 3 bed 1 bath... if they are not too old, 1.5 or 2 ton HVAC (compressor and air handler) would be the most expensive part, right?

But if you do foam a whole house or commercial building most codes nowadays require you to have an a air handler unit or a similar HRV(Heat Recovery Ventilator).

HVAC includes new furnace, refurbished air handler, new water heater and expansion tank, sump pump, and some duct work.  

Des Moines you might get an airport baggage handler.

All the copper has to be replaced, to and from the inside, and the air handler as well, in most cases, when the low and high pressure side valves are not 410 compatiable....

Quote from @Carlos Handler: Hi everyone!

@Jay Hinrichs, they do have air handlers that recess into the ceiling instead of hang on a wall.

Interesting I have been watching some that have built 'air tight' mass walls like ICF (I dont like) to the new DOE 2012 IECC code coming to all states, that in the NE cold bitter climate zone are off the grid on solar or geo, using new electric HVAC ductless single zoned called 'minisplits' some though wish they had installed another zone or two or 'air handlers'....nice about these besides being 97% efficient is each room can be set at a different temp unlike forced air that is becoming obsolete due to low efficiency and leaky ducts in unconditioned space robing u-bills.

Ended up having to evict them, but the section 8 case handler told me that usually tenants are careful to keep the landlord happy, because they know section 8 can remove them from the program if they aren't following the rules. 

Since R22 is being phased out by 2020, R-410A units are the replacement units, but from what I've been told this requires that you change the air handler as well.