grinding down travertine floors

I'm finallly going to take the plunge and (http://maplered.com) grind down my travertine floors.

I don't have the money to buy a floor polisher so I'm going to have to do it by hand (http://maplered.com) ....yikes!!!

What would you guys suggest as far as tooling? I don't have any tools for this yet....not even a var. speed grinder...I only want to take the polish up to 400 grit, then I'm going to apply some enhancer.

Thanks,

Matt W.