Useful and most bang for the buck?
Electrician. You can work while taking classes and there is a a lot of options, whether to go private or work for a company once you're a journey-level electrician. Both of my brothers are electricians and they can work as much as they want on the side along with their full-time jobs.
Next would be plumbing, but new construction would be the best place to land if doing plumbing. You never know when the construction market might take a hit also.
All that said, I went the 2 yr college AAS deal for welding and it's been a good career for me. The welding education was absolutely crucial to getting me started. I've worked with many guys over the years that went to the school of hard knocks and glad I didn't go that route.
