But on the inside, brittle plaster walls (hard to hang anything), lead paint covered by about 1/4 inch of repeated repainting, finicky radiant heating, sparse electrical outlets usually ungrounded, 100 year old plumbing, literally zero central air or proper ventilation anywhere (= upper levels are a sauna… look for a single HVAC grate anywhere), legacy window and door hardware that can’t be replaced… the list goes on. Every improvement project risks disrupting decades of toxic building materials and carefully grandfathered code violations.