As I have said before (I think), apprenticeships these days don't really exist. They kind of do, but not in a traditional sense. Believe me, though, when I say that, for the most part, that is a good thing.
Imagine this: You have a couple older brothers. Your eldest has clearly been groomed by your father to take over the family business. In this case, we'll say the business is a farm. You, on the other hand, have been doing your daily chores and haven't been trusted with much on the business side of things. In essence, you are a hired hand that doesn't get paid, but you do get a place to live and some food, so that's good, right?
In time, the family farm will become your brother's farm. Your brother's farm. Not the family farm, not anymore! I don't know about you, but not many people are thrilled at the idea of having an older sibling be their boss. So, at the prospect of having him rule your adulthood as much as he tormented your childhood (that is what brothers are good at, after all), you may start thinking of picking up a new trade to call your own. Welcome to the wonderful world of apprenticeships.
At a young age, we'll say 10-12 (if blacksmithing is your destiny, older if you want one of those edumicated positions like being a lawyer or something that uses books) you get to hit the road and be a working man. I do mean man - tough luck ladies, you don't qualify. Say good bye to your folks, you may see them a few times if they live locally (like, 10-20 miles), otherwise... well, life is short. Instead, you move in to your new master's shop. Not house, shop.
Now, I am not talking about the modern era. Electricity? Central Heating (or any heat)? Air conditioning? Running water? Who do you think you are?! You get a roof, a blanket, and something to do every waking hour. Your master will feed you out of the kindness of his heart and will likely give you new clothes every year or so, but never expect more than that. If that sounds harsh, too damn bad. The alternative is pretty much losing your reputation and crawling on back home to one day work for your brother. You could be relieved of your position, but more often than not you could never simply just "quit" - you may be required to sign a Contract of Indentures. Indentured servitude is illegal nowadays (it was kind of like slavery, but "ethical" and I use that term very loosely), but boy did people love it when you could use it. If you did leave, you would be hard pressed to find another job, let alone an apprenticeship. No one likes a quitter, contract breaker, or lazy and stupid boy. As far as the public was concerned, you would be branded all of the above.
Your duties will start out simple, but as your skills improve so will your responsibilities. After nearly a decade of sleeping on the floor, working abysmal hours under conditions OSHA would cry over, you may advance to being a journeyman. Here you are, now 18-20 years old, a man by all accounts, and ready to set out on your own. Too bad you haven't been paid for that past 10 years. Instead you get to journey to other shops, hopefully find some work, and get a cut of the work you produce (hopefully), all the while learning a few new skills or approaches to your trade. This is how the trades, and yes even lawyers were a trade and offered a variation of the apprenticeship, persisted generation after generation. No standards, no promises at success or that your master would even be remotely good/ethical at his approach. Even today, there are a handful of right ways to do things and many smiths will tell you the "best" way, only for you to find another smith claiming his approach is the "best".
Eventually, apprenticeships went the way of education and required some level of order. Trade schools came into existence, labor unions influenced education and (of course) the work place, and the "good" old days became what they are - something many think they would like to do, but few would actually ever endure given our modern approach to life. People were tough back then. 10 year olds were tougher than most adults are now. Our lives have become easy, by comparison. The good news is that you now have the time to have fun, pursue a passion or hobby, take a vacation, and - best of all - your lives are not bound by the decisions you make as a child.