How much of a financial buffer should I have before moving out of home?

Basically I'm 20 and planning on moving out of home, got 2 other guys and the rent is looking like $480/3 so $160. But there's more to it than just rent (furniture, etc.) I work pretty much 40hrs a week and make about $850-900 and can currently save about $500 a week living at home, how much did you guys save up before you left home? I currently have about $15000.