Notorious B.I.G.

Number four: know you heard this before

Never get high on your own supply

Number five: never sell no crack 
Where you rest at

I don't care if they want an ounce, 
Tell 'em bounce

Number six: that goddamn credit, dead it

You think a crackhead payin' you back? 
Shit -- forget it

Seven: this rule is so underrated

Keep your family and business completely separated

Four of the ten commandments set forth in Biggie's "Ten Crack Commandments," which was included on Life After Death, the 1997 double album that was released shortly after he was murdered.

Biggie knows what he is talking about here.  He dropped out of high school when he was 17, and within a year, was in jail for dealing crack.  He continued to sell drugs even after signing a recording contract at age 20.  His producer, Sean "Puff Daddy" Combs, ordered him to quit dealing.