He probably has a little black book of everyone who attended his freak off parties, likely including some very powerful, influential people. This might ensure a lighter sentence. Anyway. Didn't Trump say he might consider giving him a pardon?
As for restarting his music career, he is supposedly a billionaire, looked up to by many in the rap scene for whom his crimes are likely admired as part of the 'gangster' lifestyle of drugs, guns, bling, women and misogyny. Though 50 Cent isn't one of them.
I doubt he will have much trouble releasing and selling new hit music.