To become a Kage/Leader of a Village You must be at least Level 35, Other requirements will be told below:
Hokage:
Nin - 80
Gen - 40
Tai - 50
Def - 30
Agi - 30
Kazekage:
Nin - 70
Gen - 25
Tai - 65
Def - 35
Agi - 35
Sound Leader:
Nin - 55
Gen - 70
Tai - 65
Def - 20
Agi - 20
Mizukage:
Nin - 70
Gen - 30
Tai - 50
Def - 40
Agi - 40
Akatsuki Leader:
Akatsuki leader has no requirements, though I might do some investigation on the strongest people, do not ask for Akatsuki lead, Akatsuki will ask for YOU!