I prefer a rolling release at home since the new bells and whistles make me feel warm and fuzzy but for the production box Centos does the trick.
Also you shouldn't need to "buy" a server to start with, since many distros will run on limited hardware you may be able to scrounge up. You won't need much unless you are planning on running some serious Java apps.
My testing environment is Gentoo 2.6.34 Apache 2.2.15, PHP 5.2.14, and MySQL/Postgresql which all runs on an ancient dual p3 866 w 1 gig of ram.
The production box is a quad dual-core Xeon with 8 gigs of ram running the same Apache, PHP and Sql but it does more since it also runs DNS, a mailserver, ftp server, mailing list and has multiple accounts etc.
You could also install some VM software and run a virtual linux to get your feet wet.
Wheel is right, all in all the Linux distros are more the same then different but I would stick with more mainline distros if you are hoping the knowledge will get you work someday. I also wouldn't hold my breath thinking someone is going to hire you based on your playing with a nix server at home either. Work on the basics if you have absolutely no Linux experience your road will be longer but try and work from the command line as much as possible, most servers don't run GUIS, critical skills are moving, reading, deleting files, understanding file permissions, understanding basic DNS and networking, using some sort of terminal app to login remotely (i.e SSH), starting services, stopping services, restarting services and that's just the tip of the iceburg.
Good luck with your adventure.