What kind of PC should I use to run MAME?

-I'm looking for a cheap PC that I can use to build a MAME console. I've been told I don't need an expensive PC, even a 10 year old one will do. I'm just having trouble finding the right one on ebay, does anyone know what models of older PC I can get? I don't feel like spending over $100.00 or even $50 if I can get away with it.