starting a forum/website - advice?

[krick]

I'm planning on starting a website/forum similar to http://www.scubaboard.com except that mine will cater to the gay scuba community, a group that scubaboard currently shuns.  If you're wondering, a gay friend asked me to start a site after a recent bad experience on scubaboard.

The focus will be primarily the message boards, with possibly other content being added as the site grows.  Probably some sort of limited picture hosting for users.  Maybe a news/blog page.  Maybe a database of trip reports.  Maybe a wiki since they're all the rage with the kids nowadays.  Who knows what else.

I already have several decent domain names.

I haven't picked out a host yet, and I haven't picked out any forum software packages either.

I really like the way BYOAC is set up and I figured I'd ask here for advice.

I don't want to make any rookie mistakes.

What should I expect in terms of monthly/annual costs?

I use Google adsense on some of the pages on my personal site, so I have a little experience with how they work.  Assuming a respectable amount of traffic on my new site, can I expect ad revenue to cover the hosting costs once it gets up and running?

How much of a concern are hackers?

Basically, is there anything I should or shouldn't do, things I should avoid/look for, etc...?

thanks to anyone who responds