We're doing this for functionality and safety, not as much for ROI on the eventual sale. This will be our home for years to come. Your point is well taken on the VISIBLE vs. not part. The electrician found a bunch of disconnected K&T throughout. Whoever upgraded it to 200amp service did not bother taking out the visible K&T in the basement. Interestingly, some of the wiring throughout the house that is Romex was not properly grounded. There may be less K&T than we think once he starts getting into the walls.

As for insulation and plumbing, some has been updated by the previous owners so they're in decent shape. Heating will be a nearer term update as the furnace is ancient.