the average player age for mine is 12. but we even have a 7 year old playing and she is safe there. that is what i wish for because i know how some servers are to younger kids who can't even spell right..
Im a server owner who is not out to make a profit. and i have seen many others. just they tend to shut down like you said. no funds. but there is good ones out there, kind of comes with when you make a kid friendly server. only get kids with no money. but its still good ^.^
You can try out my server, lightningnetwork.mcs4.me. It is small but normally gets 15 players a day. Mainly a survival server with a few extra things, along with stuff that you won't believe unless it was modded(but is not) <3