I want to build a (cheap) server for Minecraft, UT(1999), and file sharing. Totally new to server building.

In the very near future we're going to be setting up a home server and while we've been building computers for the better part of two decades we havn't ever delved into servers. We're hoping to build a system that can handle the following:

-a Unreal Tournament(1999) server that can handle up to 5 people very well and hopefully up to 15 people to some extent

-a Minecraft server that does not lag with 2-3 people, but will also be capable of holding around 10 people at a time(with acceptable lag)

-general file storage/access

I'm also looking for a good website that will help me with setting up a server one built, including setting up and using Linux(no experience). With budget in mind we need a better idea on necessities(do we really need ECC ram or can we go with cheaper DDR3?). Right now we need the absolute basics and tips on server building so that we have a better idea on what to start looking out for on craigslist and ebay.