In a 2009 interview (above), Mel explains that he began rapping in 2004. He was on tour with Jim Jones, who heard him rap and insisted he head to the studio. He explains here that his time in the rap game started after a stint in jail. After he came home, he said, Jim "snatched me."
In an interesting bit of trivia, this interview also includes another of Mel's co-defendants, Fuguan "Fu Banga" Lovick.