@roser - For the majority of people, probably the latter. Especially if you're just starting out, being the tech guy at the local bar I imagine you'd probably get paid very little, but at least you'd learn the ropes over time. My dad did it for a while mainly because he was interested in it, not for the money. I think the only way you could make a living off it is if you scored a gig with a famous touring band which would only happen after years of experience, but nothing's impossible. Then you'd have to live on the road most of the time, but that lifestyle suits some people.
Interesting anecdote about Noel Gallagher originally being a roadie, I had no idea. It's probably beneficial for musicians to learn all of the behind the scenes stuff for when they put on their own shows.