Finished kitchens, baths, hardwood floors, plumbing, wood windows, wood beams, etc

Plumbing work typically costs much less than electrical work, so I always advise to stay away from properties that have all the wiring pulled out or, if you run into any knob-and-tube electrical - no thanks!

One of my client's is being sued creatively by an adjoining retail condo for alleged illegal or negligent installation of plumbing. 

The 4 new apartments are going to need all of the interior framing, windows, electric, plumbing, heating and also new siding for the building.

I understand the need to use licensed/insured tradesmen for electrical, HVAC, plumbing,roofing and I will easily be able to obtain W-9, copy of insurance.However, my plan for flooring/sheetrock/painting/siding is to use sub contractors that may not be able to produce a legitimate W-9, may not have insurance, etc.Is this a bad decision?

I do have a US phone number on Skype on which I talk to realtors, cash buyers etc so callers will only pay the US domestic rates, not international, so that at least is not an obstacle. 

If the plumbing is separate, which it rarely is if it wasn't intended to be.

Could be roof leak, or plumbing pipe leak, maybe a drain.

The home is old, built in 1919 with original plumbing, wiring and two major floor to ceiling cracks in the foundation.

Was taken down to the frame and new electric and plumbing was installed.