If you know someone and you get into it, you can have a pretty good career I would not recommend being a non-union pipe fitter or even working for a non-union company in any trade (except a family business) not if you want to learn and do it right and have longevity and financial security, most of the unionized construction trades usually have educational training facilities thru the union or junior college for their apprentices coming up, non Union fire sprinkler companies are basically like picking people up from Home Depot.
Note: many junior colleges across the country have programs for the HVAC trade as part of their curriculum.