How'd you wind up here
To be honest this is not a beginners forum tutt but we're all nice folks and we'll help you out anyway!
I recently helped a friend set up something similar. I assume you have a PC. Let get... er... prudent!
M-Audio MobilePre USB - $149
Cakewalk Home Studio 2004 - $89
Marshal MXL 990 - $59 (musiciansfriend.com blowout)
Not too slutty but it'll get you going for under $300!
Not sure sure if you need a mic or what, but a budget condenser should do the trick for basics.
You should go to these sites for basic information that will be more helpful to you at this point:
acapella.harmony-central.com/forums/
http://www.musicplayer.com/cgi-bin/ultimatebb.cgi
You will understand the concept "latency" very soon though!
