I could be wrong. But I think the Kagebunshin was to fool others while the real madara lived. The corpse that black zetsu provided to Kabuto was the real corpse that was from the old Madara. You know the madara that trained obito etc.
But even so your right the first Kagebunsin would have to have been alive. It probably only needed to exist long enough to the body to be buried or until people stopped actively checking on the body or corpse? But that would be horrible being that clone. Do clones need to eat, drink, breath? Do they have heart beats? Even if the clone only needed to stay there for a couple days to a week that would still kind of suck.