You need a very thick skin to run one of these. They are attacked incessantly and people will eventually try to disrupt it after being members of good standing. The worst expense is often to get things fixed after a hosting screw up.Pick you host very wisely. Keep the conflict to an absolute minimum as there will be lots of attempts to bully other members .Think about the massive amounts of time to vet membership requests and read everything each day to maintain discipline.Many of us here from the beginning remember how extremely hard it was at times. If you do not like conflict and avoid it running a site is not for you as it will fill your day with stress.
With this said, these other staff members have massive amounts of graceful patience.
You will need a solid hosting, someone that can go into your control panel on your hosting and understand it, Few hundred bucks in a bank acct to back up and repairs in the server, Patience, be tolerant of others views in life without having to condemn them for their views and accept them as they are with all their faults "like the rest of the staff do with me :)" lol!
Its a big thing setting up a website forum, those free forum websites are more expensive than using your own hosting.
The other thing, pay many years in advance for your hosting, its less costly when its time to renew.