what is diff between IBEW and apprentice electrician union and non? which is wiser choice?

in 40s planning career change to electrician.would like to know pros/cons in field. and apprenticeship. what might be the hardest about field. what you like or dislike about being electrician.whats the oldest you see starting in profession?best way to start union /non?why is the pay really going to be $$$after 5yrs? Do you think field is over crowded?