I actually have detailed pictures of my house before drywall so I remember where they put the blocking and nailers on block to more easily find it later.

Installing a traditional a/c would either be an air handler or a furnace with the ac coil on top and an outside condenser both options would need duct work.  

(they are the same) They use heavier duty parts, they were the first to use all aluminum evap coils, they have low pressure sensors/switches to protect your unit, they have been innovating more efficient motors, blower housings, electronics beyond other brands. 

He also kept trying to put words in their mouths, claiming there was mold in the central air unit, but there was nothing more than filthy looking coils that an AC tech company cleaned out.The PM is placing it in writing this morning that he requested all of his money back, we offered all of his money back, and he's refusing to leave.

My problem is going to be handing over the reins of the real estate when I either get too old or the estate when I "shuffle off the mortal coil".

When we send a tech out they usually find dirty coils and a dirty filter if there is one at all. 

With 6 houses we own the warranty has replaced 1 water heater, 2 ac coil and coolant recharges, 1 ac power line, 1 refrierator, 1 electrical outlet repair (tech found a short in the line we missed), 1 stove/oven control board and 1 furnace repair, all in the past 3 years.

I own an 18-gauge brad nailer/stapler with a small air compressor.

One of those empties had the AC/furnace coils, water piping, main electrical panel, and water heater all stolen.

Stick to basics...free standing self cleaning ovens with coil stove elements; refers that do no have through the door water or ice; and if possible (more and more difficult to find) no "digital" touch pads.