Mad Max, zombie apocalypse prognostications are generally dismissed as chicken little paranoia for good reason. Unfortunately, the speaker automatically loses credibility and doesn't accomplish anything useful. The smart play would be to be quiet, bide your time, and be prepared like a Boy Scout. I seriously doubt anyone saying civilization will ever disappear because there are too many incentives and advantages of division of labor and trading, but life for most common people will gradually become rougher, harsher, more expensive, and increasingly upheaved by temporary disasters. Periodic famines and long-term food costs will sneak up over time are more likely.

If someone wanted to invest in OTG self-sufficiency, then they would need a remote, defensible homestead with wind and storm resistant agriculture and a durable water source. It's a waste of time and money unless someone enjoys the catharsis of microfarming and already has plenty of money.