My son said he wanted a dirt bike, so I told him he'd have to save up for one himself.
I was hoping he'd either say "Forget it", or he would start and then give up - or at
least it would take him a long time.
It's not that I didn't want him to ride dirt bikes, but I know he can only ride around
on our property (1 acre) for so long before we'd have to go to a riding area.
Not that I would mind riding dirt bikes (again, as in my early adult days)...
and I know my wife and I would have fun riding... it's just that we have too many
activities already. I'm not so sure I can get my daughter to ride one either (she's
about 1.5 yrs older than my son, but a bit timid about sports which could involve pain).

So I told him to start saving his money... Well, he saved up about $500, and started
looking on Craigslist (actually, he started looking before that even).
He was like a Chihuahua on a porkchop - not gonna let go!
He found out that with about $650 he could afford a decent 80cc bike. Then my daughter's
basketball coach suggested a Yamaha PW80 would make a good first bike, and offered to let
him come over and try one out. He found a couple of PW80's he can afford... and rode the
coach's PW80 - Eventually he saved up about $700. We found a fairly new PW80 that had
sat out in the rain for a year or two. We got it for around $300, and I taught Drew
how to rebuilt the carburetor and take everything apart to do the neglected maintenance
an repair damage from exposure to the elements (there's a couple of pictures of him working
on it below).
So, it looks like we're gonna start another new hobby.

These pictures are the evolution of that new hobby...