We live in Japan in an urban environment- lots of big apartment building around. The house is post-war house that extended and has an antiquated arrangement whereby a rich person owns the land and we have an informal agreement so we don't pay anything. The rich person died and his son inherited it and after some conversation he agreed to continue the arrangement. I would think anyone would be insane to pay anything for our house- they couldn't be sure that the land owner would keep the arrangement with my wife's family. Of course there is the devil in the details of valuations, but the land is probably worth a lot.
Judging by equivalent situation is our house nearly worthless unless we can shore up some formal legal arrangement with land owner?
Update at 8th March 2023: Father-in-law bought the land but neither told anyone- he is borderline comatose. Mother-in-law was financial ignoramous.