Keep your eyes open. I have a feeling that you will be able to get your hands on a used G4 system at a good price soon that will run all the iLife apps. I have always made good use of iLife, now that I have iLife 04, that tradition will keep on going. I love every click about it.
If you can afford the slowest G4 Sawtooth (it has AGP graphics), that's the way to go. the upgradability of this Mac is better than the B&W. You can stuff a dual 1.4GHz G4 processor in it if you want, and upgrade to a much better graphics card.
As stated by others, Apple is dropping OS support of any mac that does not have built-in USB.
right here on ehMac is a good place to start for used stuff, also the sponsor dealers like MacDoc or Carbon
or end of line stuff can be found at big name stores
I do not suggset buying Macs on EBay unless you like to gamble