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). 

Ducting is already in place, so in that scenario we would normally opt for a centralized heat pump (both heat and air conditioning), but have used gas furnaces with a an air-condtioning exchanger coil in the plenum and the compressor outside.

I had them install the A-coil on the furnace and plumb the lines for future central air in the event I decide to go that direction. 

@Gary Wallace for less than $25 you can buy an electric griddle and you can buy electric table top coils for $12 a piece, which will let you use standard pots.

The special rod he has will be inserted into the sprocket hole and he will crank each side until the coil or spring inside is tensioned correctly for the door to operate smoothly.

Bad heat exchanger on a gas unit (CO), mismatched heater/AC and coil.  

Ac guy says nothing obvious in the ac but wants to charge me $380 to clean the coils tomorrow. 

You can 1031 your properties over time until you get to a point/age where you either want to diversify out of REI or just want to get your ducks in a row estate-wise (say when you've got about 20 years left on this mortal coil).

If they are still there in a week, coil up what is in your yard and place the end of the hose at the fence line pointing into their yard.