I realize that I'm asking a very general and ambiguous question, but I
really have no better view of my plumbing problem than someone reading this
for the first time. So let me just say, I'm only asking for educated
guesses, not precise answers.

We live in a six-unit coop apartment building, with two units on each of the
first three floors.

The top floor has six dormitory-style rooms which once served as the living
quarters of servants -- one for each unit, I'm sure. There was a bathroom
at one end of the hall, a kitchen at the other.

In the 1950s the fourth-floor was converted to storage rooms, and the
plumbing was disconnected.

So to get to the point: I'd like to reconnect the plumbing so that we could
make these rooms habitable once more, to be used as guest rooms.

All the connections are still in place, with pipes capped off. I'm sure the
old pipes were left in place, but I'm also sure they're rusted completely
shut at this point. So replacement of the pipes with copper is no doubt the
starting point.

The bathroom that we want to reconnect is directly above the main water
supply in the basement, hot and cold.

My question is, are we looking at a fairly simple and easy project?

Or can we expect a five-figure layout which would involve tearing out walls,
etc.?

As I said, all I'm seeking is educated guesses.