Our children's first in our home sleepovers took place at around age 8 and as far as sleeping away from home the age depends on how well you know the family whose home they'll be at. My children are not allowed to go play at anyone's house unless I know the parents and some of their school friends are the children of close frineds of DH & I so we have always made sleepover decisions on a case by case basis.
My son is 6 and hasn't had nor attended a sleepover yet (unless you count g'ma's and my brother, but it's just him or him and his sister that spend the night).
My child hosted his first sleepover at 7, and has been going to them ever since.
I never knew boys liked sleepovers so much, apparently times have changed since I was young. I don't recall my brothers ever having or attending sleepovers.
They have been sleeping over close friends houses since 1st grade. Hosting started about age 7. We have an entire collection of toothbrushes that belong to their friends, that tells you how often we have kids over here.
Thanks for your replies. It looks like if you average it out to be about 7 years old. My DS just turned 6 in June and has been begging for a sleep over and DH and I have told him he is too young, but it lloks like he is close to the average age. The only sleep over he has ever had was at Mima's and Pop-pop's house.