you should have said to your silly BIL that I'll bet you a large wager that the big A wont be here in months/years let alone weeks!
Someone on this forum had this idea: pressure the person to commit that the big A will come in at least the next two decades. Then tell him you pay him $100 (or $500 or something you consider worth it) now if he comes to an attorney to sign a paper telling he sells you his house after 20 years, for $1. This is not a bet, so he can't decline saying he doesn't gamble. Armageddon will come before that, so he has nothing to lose.
Edit: never mind, I just realized he's a bethelite... he's probably broke and has no means to support himself, or where to live outside Bethel.