Assuming you don't want to spend too much money, I would buy a USB interface (try to get a firewire if you can). The M-Audio firewire 410 is pretty good. Then you need a condenser mic to record the vocals, and a pop filter.
It depends on what instruments you want to record. You can record acoustic guitar with your condenser. If you're going to record electric guitar and bass, then you'll need a dynamic mic, I heard the sm-57 is pretty decent for this. Here's the hard part, if you want to record drums and want good quality, then you'll need many drum mics. I would personally just program the drums with Propellerhead. That's actually what my band plans to do.
Last but not least, if you're going to record a keyboard you can just plug it in to the interface and get studio quality most of the time (unless it's a very dirty sound).
You should post your budget and your quality expectations. It's not cheap. I first had to buy my interface, waited a few months and bought the mic, etc. Take note that I was 16 when I was buying all this
I'm sure you can afford it easier if you have a decent job.