Always tricky with forums Rob as they are very taxing, bandwidth hogs and open to abuse from hackers (php injection, false hotlink accounts etc), I've run a few in my time, I started on Wildcat BBS before "the internet".
Problem with hosting yourself Rob is those people who are "helping" you pay for the server via their sites will start to treat you like any ISP when it goes down or there's a problem with their site/email/computer. Doesn't matter if you've charged them £25 a year they still treat you like they've paid 10K. Made that mistake myself and seen it happen to lots of people, my advice is don't do it unless you enjoy being IT support
Why not just find a good vBulletin host and perhaps organise a STB series of shoots across the world to help raise funds for the resource we all use? I'm sure loads of people would help organise that.