Home Server/Dedicated Game Server

I'm looking to build a home server that I can use for a dedicated server with games (COD4, CS:S, etc.). I have no clue on servers so bear with me.

All I really want is to be able to host up to a 16 person server that is stable. With comcast I can get quite a bit of bandwidth - how much would I need? I do realize i need decent up speeds, down speeds are not a problem with comcast... what type of total bandwidth do I really need?

As far as the system- I found a very cheap barebones set-up featuring a Pentium D 965EE (3.73ghz) and 4 GB PC6400. Would that be enough power to keep it going. I realize that Pen Ds are ineffiecent and old tech but for under $200 and only needing HDD and Op Sys it seems like a good deal.

Now that I probably sound like an idiot (again I have no idea coming in), can you guys give me your advice for (cheap) builds, what type of bandwidth I would need, or is this even possible for my intentions?