Do any of them use chemicals, any corrosives, are operations expected to be loud or cause noise issues?

Down in the basement I go, armed with bee randy new fuses, I pull the mains, move the cigar fuses a little to break any corrosion, screw in the bee randy new fuses, and voila, problem solved.What kills me is that the old fuses look and test fine.This has happened damn near every time.Had to do it again today.Cue Rod Serling and the Twilight Zone music...

The condensate drain and trap need to be cleaned, and the water replaced in the trap.The blower wheel needs to be checked for debris and cleaned if necessary (this requires complete removal of the blower wheel).An amp-draw test should be conducted on the blower motor and compared with what is listed.The wiring needs to be checked for corrosion and damage.The filters need to be checked

this is the scope of work. the dimension of the roof is roughly 45X151) Tear-off all layers of roofing and gravel down to wood decking and legally dispose. 2) Inspect wood decking and replace all deteriorated and broken areas at $ 2.50 per sq. ft. 3) Inspect existing Ceramic Copings and replace all deteriorated and broken at $ 35.00 Each.4) Install Fiber Cant Strip at the base of the walls and curbs.5) Install 1 layer of Base Sheet over wood decking using corrosion resistant screws and plats. 6) Install 1 layer of Modified Bitumen CertainTeed GTA Granulated. 7) Install Metal gravelstop and gutter flashings at the roof edges. 8) Flash all vents, soilpipes, and chimney using the same Modified Bitumen. 9) Install 5” Galvanized Box Gutter and 3x4 Downspout to replace existing. 10) Pick up and haul away all roof debris generated by Presidential.

Galvanic corrosion occurs wherever two different metals touch.

This can lead to additional corrosion w/in the pipes, possibly leading to premature failure of the heat exchanger, which is not inexpensive to fix as I just fixed one on one of my properties.Assuming you're on gas, you could (imo: should) install a condensing gas boiler.

The rotten egg smell is an indication of hydrogen sulfide in the water which can occur naturally, but is very corrosive and can cause problems with plumbing and fixtures. 

Don't forget also to replace the corrosion rod every five to ten years years to extend the life of your water heater.

@Philip Nowak go to Home Depot and by some corroseal rust converter. 

Unfortunately, we have corrosive water in our area, so we experience some issues more regularly than in other markets.