You need to make a solid base at the start. With well known members.
Divide the responsibilities. And no one should have full control of anything.
All decisions taken by vote help to keep things fair for everyone.
You will get some black sheep at some point. We had some and we might still have some. So sometimes we need to cut a branch in order to keep the tree alive. At the end of the day you have loyal and serious members who become real friends. We help each other in many way that goes way further than just lab test and bodybuilding.
Honestly do no close the door to "rookies". We got some really nice members who came with no online background.
However we created a secondary group, kind of a closet, for totally new guy. They usually stay there really short, just the time to get to know them. At this time, we have 0 member in this secondary group, and try to not use it as much as possible.
You will get some troubles along the way. They are natural disasters, no big deal. Because you will always be able to count on your solid base members.