linking eMac to home network

I'very been given an old eMac. Works very well, and I want to use it as a back up computer, putting it in a shed. So I need to link it in to my home network. I'd like to do this with a USB network adapter, and would be grateful for suggestions. The Mac is a G4 /1.42 from 2005, so it's got a USB 2.0as well as FireWire ports.