Who smart is he?
Does he want a traditional trade or a modern trade?
If he's normal smart, there's a lot of good advice in this thread. Industrial HVAC, Electrical and Plumbing pay very well around here.
If he's on the bright side and wants a modern trade that is best achieved with after a 4 year degree, I'd suggest Data Base administration, or some kind of engineering, Petroleum, civil, electrical. If he likes math, there's a hugh demand right now for good Data Scientist as well.