If I recall correctly (I was very young), my older sisters chose to move (well, eldest was asked) to our grandparents' at 16. Having just turned 18 myself, I've been contemplating this topic. I've been reassured by my mom that I may stay as long as I'd like. I don't have college plans yet and I plan to apply for Disney, so...I don't see the sense in moving. I can't take care of myself financially, and, believe it or not... I LIKE my mom and she likes me. I don't
want to leave.
I know some people don't like their parents and run away ASAP, but if your family is cool with you staying at home I don't think it's a wise decision to move unless it's for college or a stable job. The way I see it, parents should help their children and teach them important lessons in their first years of adulthood. I don't know about anyone else, but I think this will be the time I'll need my parents wisdom the most. I simply couldn't fend for myself if I were kicked to the curb.
When my sisters moved back in, my mom charged them rent, but they worked and didn't do any household chores. I clean, cook, care for the dog, garden, coupon, and make my own cleaning, beauty, and food items to help save money. I'll run errands when I get my license. So, I figure that's my form of rent. I'm sure I'd be charged rent if I moved out and came back, but I'd still be happy to do housework. If you bothered to teach your kids basic life skills (it's becoming increasingly rare, unfortunately), you just got yerself a free housekeeper.
I've heard stories of kids coming home on their 18th birthday to find their stuff packed away in the driveway without warning. That's cruel on any level. How is that teaching them a good lesson?
It's one thing to encourage them, like Yuna said, but kick them out at 18? I'd never do that to my own children, even if I ended up hating them.
So, no, I don't believe it's the right thing to do if they're not ready.