I'm not sure what the rest of the US market is like, but the Bay Area has a huge shortage of tradespeople because of the 2008 housing crash and very high cost of living pricing folks out. I knew of this but became much more acutely aware when I started doing transit advocacy. Getting folks to build/maintain HVAC systems, weld, drive buses, etc is getting increasingly difficult.

If your son can avoid having to buy into the Bay Area housing market (by living on property you own/pay for), he can make good money and probably will have little trouble finding work for years to come.