From what I remember, the G5 iMacs are notorious for leaky capacitors on the motherboard. That's probably why they're cheap on ebay.

If yours really works, that's cool. You could make it a file server if you hook up a big drive via Firewire. I wouldn't want to browse the web on it, but someone might. You can still put current versions of LibreOffice on it.

My last dealings with a G5 were in 2009 or so, and it was showing its age then. Just keep in mind you're working on a machine that was competitive with Pentium 4s. Even a fresh Windows XP install on a P4 PC would feel like a dinosaur by today's standards.