What version of Mac Mini supports Leopard 10.5.8? Does Leopard 10.5.8 support the first-ever Mac Mini (M9686*/A, M9687*/A, I think)?

Or do I need one of the later ones?

I'm buying my first-ever mac this Christmas.
Yes Leopard supports all Intel and all PowerPC based machines over a minimum CPU speed and the original Power PC minus are in that ranges. Apple doc

Snow Leopard (10.6) only supports Intel based machines