In California if you are a plumber, roofer, HVAC, electrician etc you can make six figures. If you own a small contracting business in one of the above fields you can clear $400K a year, tax free, for like 6 months of work. The real estate boom in CA combined with a shortage of skilled blue collar labor means that if you have these skills you literally have a 2-6 month waitlist for your work

I know some people who grew up in very low income situations, in and out of jail, but took an HVAC or plumbing course and are now making $150-200K at age 25-30

Of course this is definitely not recession proof but I was super surprised to learn this