I bought a new-construction place, and I was around during the process. After they were done with all the plumbing/wiring/etc, but before they filled in the insulation and sheetrock, I walked the whole house and took cellphone pictures of every bare wall to show where all the pipes and wires are run, and then labelled it all up by room. I plan to hand those off if I ever sell the place! I don't know why builders don't just deliver such a set of photos to everyone by default, it's been super handy!