Disk space for vbulletin

Hi, One of my friends is planning to run a community using Vbulletin; what disk space he will require for hosting and monthly transfer rate is normally required for that. I have checked on  http://www.halfpricehosting.com/webhosting/windows/devadv.asp and http://www.ehost.com/ehost/hosting.bml these offer from 500-1000MB with 20GB monthly transfer rate, is this enough? Or there is any better low cost and effective solution?
Thanks