system
A chat on subreddit /r/wallstreetbets
human
The HELOC situation can be prevented if you maintain ownership of the house along with the loan...  putting clauses in there preventing it.  As far as turning it into a shooting range? No answers there lol... but you'll def have some legal expenses while you try to sue him... best bet would be to buy a house that already has a good amount of equity before you even buy it.

gpt
In what world are you expecting to get money out of a suit against someone like that?