Through my source's suggestion, he learned welding through unions because they offer some of the best specific welding opportunities out there for not only learning it but for getting a job as well. And, doing so, you get paid to work through learning it.
One of the thing's my source suggested about knowing what to expect would be related to work ethic. Oftentimes, the job can exceed long hours and need attentiveness throughout those long hours.
I'm a professor of English, but my father has been welding for over twenty years, which is where I am getting this information.