Should we re-do all the old electrical wire in a Philly reno?

[Nikki Taylor]

My partner, a GC, and I are involved in our first flip in Philly (Girard Estates area) and we're trying to decide whether we can keep the some of the old wiring in the house or whether we need to completely re-do it. It's old cloth-bound wiring, I'd guess from when the house was built in the 1920's. Right now, everything works just fine. An electrician we trust said that as long as the wiring looks to be in good shape, and is working, we can keep it as long as it's holding only 15 amps and we re-distribute heavier loads to new wiring (like in the kitchen, for example). That would certainly be helpful as a lot of the wiring is currently behind plaster walls.

My question is this: if we keep some of the old wiring and it one day causes problems after the sale of the house, are we liable for any damage? Is old cloth wiring something we would need to disclose before the sale of the house? Any other considerations we're missing here?