The (7) things I would recommend at least to get you started would be:
Turntable - This is essential if you plan to be a sample artist. You can still rock CDs or whatever else tho once they are converted to 16/44.1.
Phono Pre - You may or may not need this depending on the turntable you get. I believe you get better signal quality from using one however due to its built in RIAA EQing so its something to consider.
2gig CF Card - You gotta have somewhere to save your beats to. These things can be purchased for really cheap prices so I would just go with the full 2gigs or even get (2) 2gig cards and youll be straight for at least a year.
128mb of RAM - You'll learn fast that if you start to do large arrangements with big sample libraries or simply require longer recording time in stereo then youll want to upgrade your RAM. It also improves your processing performance in regards to effects as well.
Reference Monitors - If you dont have these your going to be listening through headphones for a long time which will suck.
Good Cables - Its not highly necessary to cop good cables but I noticed a drastic improvement in noise reduction once I switched from my shitty HOSA's to PROCO's.
Lots of Vinyl - This is the heart of where your inspiration and sounds come from so your going to always need to go digging for new "tools" on a regular basis if you want to keep things fresh.
In the future your going to want to expand into purchasing:
*A good music computer
*A decent soundcard with enough I/O to accommodate your tracking
*A DAW that your comfortable with
