Where does all the chakra needed for the reanimated shinobi come from? It certainly cannot come from the caster, because the scale of the chakra being used for techniques is huge. In Kabuto's case, he was controlling several Edo Tensei shinobi at once. So all the chakra they were using couldn't possibly be coming from him.
Also, when Madara broke the Edo Tensei's contract, he mentioned about "limitless chakra". Where did the chakra come from?