Well, you'll want say 256-512mb dedicated ram (we use 384mb ram with a 1gb swap space) and say 10-20gb space? Depends on your needs really...
I myself prefer CentOS for servers (it's a debranded RedHat Enterprise Linux, some places may also have Fedora which is also a RedHat varient).
If you use CentOS (or a redhat clone) it's as easy as typing: yum install apache, etc. You may consider hiring someone to setup the server for you...
Myself, I prefer using Google Apps for my email; think of it, your server goes down you're screwed for access; whereas google has numerous backup servers (and it's free, and you get like 500 email accounts with pop3/imap/smtp); which frees up your server from having to host email (and spamfilters).
I use Webmin and Virtualmin to manage my server; why? they're free for starters

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as for costs, well, if you hire someone to setup your server there would be that, but picking something to run it (server software other than webmin) can cost...