I have a potential client who wants to set up a forum like WHT for sports subjects. What amount of space/bandwidth should i expect them to use and where could i advise them to obtain more info. on WHT's particular type of board?
It all depends on how big his forums are, like he said.
Also I would avoid perl based forums as they tend to eat more resources/bandwidth. Keep it with php/mysql forums such as UBB.Threads, vBulletin, phpBB, Invisionboard, etc etc. But just as an idea here are some numbers from two of my forums.
phpBB: 2600 members, 50,000 posts. DB = 28mb and the site does around 9gigabytes/month UBB.Threads: close to 600 members, 50,000 posts. DB = 18mb and the site does around 12gb/mo, forums alone do around 7-8gb/mo.
So as you can see those are some pretty equal numbers. Both sites are have close to the same amount of activity per day so those numbers will be something to go from. Hope that helps some.