You can find videos/articles online on how to get the basement dry, but the basic process is: 1) turn off all electric to the basement (to avoid electrocution from the water), 2) run pumps to get the standing water out of the basement (sounds like you're already doing this)3) remove all furniture and items from the basement,4) once you've pumped out the standing water from the basement, rent a wet/dry carpet cleaner/extractor from home depot, and use it to extract as much water as possible from the carpets (they'll be much lighter and easier to move once you get the water out). 5) After you've used the carpet extractor to get most of the water out of the carpet, remove all carpet and get it out of the house for drying (if you're trying to salvage the carpets), or throw the carpet out.

The building itself contains a bathroom with fully functioning plumbing, electrical, and an HVAC system in place already. 

At any point any of these bad actors - whom this country likely has no clue who they are or what their intentions are - can do something drastic not limited to attacking our power grid; and most Americans aren't prepared for no electricity.

And if your electric contractor is one man, he likely can't put the 40 foot service line back on the building.If the tenants are on a downward spiral they won't get out of it even if they rationally can. 

Here's what the quote covers:- Conversion of 2 bedroom, 1 bath main house to 3 bedroom, 2 bath (~1040 sf footprint)- Demolition of existing walls (existing dining room wall, wall between kitchen and living, bathroom closet)- Finished Shell (Reframing opening to living room and kitchen, shifting openings for bathroom/bedroom, new walls at bathroom and dining, level - Replace all aluminum windows with fiberglass windows and screens- Upsizing plumbing, and relocating fixture locations as necessary- Upgrading electrical panels- Assume heat pump and ductless mini-split for heating and cooling- An allowance for kitchen appliances including combination range, hood, dishwasher, microwave, refrigerator, and washer/dryer- An allowance for mid-grade plumbing and lighting fixtures (Delta, Kohler, or equivalent)- Mid-grade plumbing and lighting fixtures (Delta, Kohler, or equivalent)- Ikea cabinets or equivalent with solid surface countertops, includes island- Assume solar system to be installed on the house including battery storageFor the garage ADU, the garage would need to be demoed and rebuilt, but we would benefit from building within the setback since the garage is on the property lines.

Instead I have decided to add some extra electrical outlets and put in lights and rent it as a workshop.

It will be dependent on how much cutting they have to do and coordination with other MEP systems such as electrical and HVAC.

I haven't seen anything under 200-250k all in cost  Part of it is detached garage and using existing structure + existing electrical.

They said the building would need to be updated for plumbing and electrical as it was 65 years old. 

When it comes to anything major like electrical, plumbing, or structural...I think you need a permit.