I understand your overall concept, for real, unpredictable one-in-a-million catastrophes.
But this is slightly different. So the wealthy swoop in, buy cheap, and renovate. GOOD. LET THEM. They will pay a lot of money to poor workers in need of jobs, pay INSANE costs to insure, if anyone will even insure them, and then climate change will wipe out their house too. Rinse repeat until everyone gets it through their thick skulls it’s a problem not to be fucked with.
Or said another way, if you want the government to support the poor people who lost their homes, do it by helping them relocate, not help them rebuild their castle so it can sink into the swamp again.