Re: When did/would you let your child go to a sleepover? (non-family)
DS#1 was 8 when he had his first sleep over. It was with a family we have known since he was three, so five years at the time. The mom is a nurse, and I felt very comfortable with it. Since then he has only had sleep overs there and with one other family who I also know and am comfortable with.
DS#2 is seven and so far his only sleep overs have been at my sister's house with his cousin. He and a friend have talked about it several times, but I don't know that friend's parents well enough to be comfortable with it. He does have two other friends who I would be comfortable letting him stay with, so he may end up having one soon.
In the situation the OP poster described, it would be a definite no from me.