You will enjoy BIAB ! Go for it.

If you don't have one already, you will need some sort of audio interface to be able to record into REAL BAND (part of BIAB purchase) or into BIAB itself.

I have few I'm selling over here:
http://www.pgmusic.com/forums/showflat.php?Cat=0&Number=352908&an=0&page=0#Post352908

Agreed though, buy the most you can afford. At some point you will like having all the styles and Real Tracks available.

Good luck and let us know how it goes ?.