Union apprenticeship sign-ups near Boston

I heard of an apprenticeship with paid on-the-job training for people changing careers. This is my first time dealing with any of this. The application needs a diploma or equivalent, a driver's licence and a short aptitude test. What do you wish you had known?

The aptitude test was mostly maths and reading a diagram. Free practice tests online were enough for me.

You earn while you learn, but the first year is tight. Plan your budget carefully.