My answers:
1. 18, and voluntarily after that
2. yes... but when? I go more for pushing responsibility rather than departure.
3. yes. Starts very early... elementary school in some cases
From my perspective, a parent's job is to raise a child who will become a healthy, responsible adult. That means that the child should develop increasingly better life skills, from the basics (cooking, cleaning, etc.) to the advanced stuff (paying bills, managing finances, and so on).
As a parent, I want to protect my kids. I see a lot of what they do, and I can see the likely results (goofing around on a swing and fell off? well, duhh... [img]smile.gif[/img] ). But I also need to let them make mistakes so they can really learn from them.
I've seen too many families where the parents don't let the kids finish growing up. I went out with a girl once whose father did the taxes for everyone in the family. It wasn't because he was a knowledgeable tax person or anything like that; he'd just been doing it forever, and no one else knew how to do it. A lot of the cult-like organizations follow the same principals -- you aren't capable of doing it yourself, so I'll do it for you.
In some ways, it can be hard for a parent to acknowledge their kids have grown up. Call it "powdered butt syndrome" -- you can't really take anyone seriously whose butt you have powdered and put into a diaper. At 23, their "kid" is still young and needs their guidance and direction. If you ever want to have fun, ask the domineering parent what they were doing at the same age... odds are it's a whole lot more than they think their kid is ready for.
For reference, my dad thought I was too young when I got married (25). But when he was that age, as my mom pointed out, he'd been married three years and had two kids. Heck, I was a late bloomer compared to him!