That's the art of being patient. Try learning those new 12 year-old kids a thing or 2 about achievement while they're in your server. The more mature players are not likely to ask for free stuff - they're either good players who want to see if the community is comfortable for them or complete assholes who don't care about your server anyway.
I used to play a server which had an awesome community. When I 'retired', I had practically achieved any possible rank (430 USD Donator, Administrator, and the unofficial Veteran rank). In the 4 years I've been active in that community, I've seen a lot of immature kids grow up in respect and wisdom. Some of them have even proven themselves worthy enough to become a part of the staff team.
It was the most comfortable, mature and the nicest community I've ever been part of. The things mentioned in this thread should be as natural as they were for that community, otherwise you shouldn't even bother starting a server (in my opinion).