Nooooo!
I would not recommend PowerPC anymore. You very likely loose the upgrade path to Snow leopard. Most of the PowerMac G5s are developing serious failure rates nowadays, too, especially the watercooled models. This seems to be one of the first generation Powermac G5 (2x2Ghz).
But if you need to because of its expandibility, don´t spend more than US$600,- (which I would see as the maximum amount of money spend on this machine on CraigsList). Don´t buy it if you want speed. Grab a Mac Mini instead, MacBook or imac.
Used first generation Mac Pros price around US$1600,- on eBay. Or see it the other way round: For US$600,- you can get a Mac Mini, which speedwise eats this Powermac in no time (but looses in terms of HD/PCI expansion, though).
This offer is trying to trick you into buying it wickedly overpriced. DON´T DO IT.
If you are willing to spend around US$1500,-, then buy a used Mac Pro or a fancy 24 iMac.