Depends, its not usually the 10/hr guys I worry about, they are a dime a dozen. I don't really expect consistent work from people making near minimum wage. General guys that do stuff like set a toilet, rough in a window, set a bath tub, reframe rotten wood, etc have started at 17 an hour. Trades get more, about 25-30+. I've been using subcontractors to do some of the work while getting my own crew together. I'm beginning to think its not worth the headache and just keep working with contractors to get the job done. Then I wouldn't have to worry about employer requirements and such.
My main point with my first post is that it is not age dependent. From my experience, age hasn't been a factor at all regarding work consistency or ethic.
As for my skills, I tend to enjoy the finish work the most such as built-ins, trim, coffered ceilings, crown, etc. I do a bit of everything though. You have to be familiar with everything to manage the build, but I tend toward carpentry the most. Don't care to do plumbing or electrical. Exterior work is okay.