The problem is of course mostly the roofline breaks, which looks a lot like a false facade.

Is the building facade in decent condition?

It has a strong entrance facade, and separates the four units well.The prominent staircase obviously takes over the entire facade, but I don't think that's necessarily a bad thing...

Can the electrical conduits/wiring for the ADU be run under the primary house's crawl space up until the house's facade facing the ADU and finally underground for the remaining bit?

A typical project would involve a facade replacement, building mechanical overhaul or upgrade, vertical expansions, new or modernized elevators, restrooms and lobbies. 

You're going to want to take a close look at the lifespan of building systems, the facade, roof, boiler, etc.

Not $2,700 worth of difficult for sure and I could do it in 2 days max including assembly of the cabinets.Had a bid for $800 to tear down the top 2/3 of the brick facade; took us 1 1/2 hours with a hammer drill.Bottom line, hiring contractors would probably eat away about $20k in profit if I hired them vs DIY. 

How much would you expect to pay for a new brick wall, say 2 stories?

Or are you asking now because you soon intend to engrave the name in granite on the facade of your company's headquarters? 

@will g. thank you so much, it just gets hard to continue to put up the facade in front of your family when something is, actually, mentally breaking you.