All good points. I'll add that the company that wanted to charge me tens of thousands to put in all those features were saying it was a groundwater issue because they wanted to make money, but they were lying to me. They were essentially salespeople, and they didn't get paid unless they did work. The home inspector, meanwhile, who I paid and who wasn't beholden to any construction interests, gave me the correct diagnosis. There's an important lesson here that's especially apt for construction; always get independent advice. The few hundred it'll cost you is absolutely worth it because the typical cost of construction is so much more.

As for code compliance -- like pretty much all houses in the area, it was built in the 1950s, so it didn't have any of that stuff per code. It had been substantially renovated recently by people who clearly were not following code and/or the permitting process and who fucked all sorts of things up (including the grading of the foundation; they had actually made it worse while doing unrelated landscaping). I also had some "fun" issues with unpermitted electrical work. If I had to guess I'd say that it could be over half of all work that isn't done correctly. So definitely don't trust it. Have someone who reports only to you looking over everything (if you don't have the knowledge yourself).