This will keep your equipment in good shape, make it last longer, will uncover potential problems, and may potentially keep you from a costly night/week-end call-out.At minimum, this check should include about 20 or more items, checking the capacitor, amp draws of your fan, compressor, pressure check, air flow check, inspection of electrical components for corrosion/pitting, and many other things. 

According to google: "Corrosion of the copper tubing in thecoil from the outside in is the most common cause of evaporator coil leaks.

He noted there are corrosion and rust in the waste lines, so there might be some leaks there, but because utilities weren't turned on, we couldn't tell for certain.I completely agree with you that there are probably more mold than meets the eye.

They treat the water to prevent corrosion and therefore limits lead.

I check the electrical panel box for size and visual defects (corrosion, scorched wires).

The service rep did tell me that the thermostat was prob miscalibrated over the years due to corrosion and use.

This liner is used primarily to protect the steel pipe from very corrosive enviornments.

A visual inspection to make sure that there is no slow leak (evidenced by corrosion) that would prevent it from working in the event of high temp or pressure is all I would recommend.

All treated samples showed the same results as the known good drywall (no corrosion) and the untreated samples matched the bad drywall (visible corrosion).

The beach sand over time is corrosive to the concrete.