I've hosted MANY forums on my servers over the years and not a single one of them has required a dedi or VPS. A lot has to do with the software and how many database queries are ran per request and such. It also has a lot to do with the servers that are used also. If you're placing a forum on an oversold, overused server, then it'll run like crap. All of our servers are NOT oversold and never used beyond 80% capacity. All of our machines have at least 4 GB of RAM minimum and are quad core xeon machines. We've never had any performance related issues. A simple shared account with a gig of space or so would be more than sufficient for this request. As the forum grows, so can his plan that he's on. A VPS or dedi would NOT be practical here, at least not in the beginning.