Hire, then train them for a long period of time? That is an apprenticeship. It's what they do in the trades already. There aren't enough slots (union or not).

e.g. http://www.calapprenticeship.org/programs/electrician_appren...

You need a diploma, a smattering of algebra, a driver's license, and the physical ability to do the work. Everything else you will be taught on the job, while being paid.