Apparently there are five basic types of plumbing pipes per this article with copper being fairly common.

I will agree though there is a nonvariable time to plumbing, power installation, etc 

Some people will live in a place with leaking roofs, no heat, leaking plumbing, etc.   

We didn't get into the depth of details I'd like but I did talk with him enough to get some basics:*25-30 properties  Mostly SFH, with a couple commercial and MFH  One 30+unit complex rented out weekly as efficiencies*5 employees    Most are laborers   All maintenance is done by owner and employees (Roofs, plumbing, electrical, you name it)   Bookkeeper recently quit so books are a mess....not sure how bad but I know everything is done in cash with paper receipts.

We are closing on Multifamily in Kansas City, MO site on need on some major renovations (basement, plumbing, painting etc), any good general contractor recommendations?

-I then take the approved architectural drawings along with any specialist permits (such as electrical, plumbing or sprinkler) to the Construction Code Office of Jersey City in a folder/jacket.

Plumbing and electrical experience is a plus but not required.

The second floor hot water tank also needs replacing so I figured now would be a good time to get quotes and see what can be done (side note, I just had to pay a few hundred dollars to correctly separate the hot water as some plumbing was crossed). 

Certain trades electrical, plumbing, HVAC that have their own licenses will have to pull their own permits due to their license.

Most inspectors will want to peek behind the walls and you may have to pull all the drywall so they can see all the framing, plumbing, and electrical.Definitely adjust your numbers on the deal ignoring that square footage and subtract any costs that may be associated with demo or corrections from the purchase price.It might be worth just getting a preliminary inspection done by the city just to give you an idea of what it will take to get it approved.