I would raise your moral and ethical objections to your friend and appeal to his conscience. If he’s unmoved, I’d walk away and find other friends.
Also, an essay that worked three years ago might not work now. What colleges and universities seek changes all of the time. Perhaps the theme he developed has become stale and trite.
It is also possible, as suggested above ˆ, that being admitted on the strength of somebody else’s work, will make him feel inadequate and like a fraud and will taint his experience. Is that really worth it?