Depending on the details of the deal, this may make Dr Dre hip hop's first billionaire.
Also - what does Beats have to do with his career in hip hop? Hip hop didn't make him almost $1bn, an electronics company he co-founded did. It just irks me every time I see 'hip hops first billionaire'. It has absolutely nothing to do with hip hop.
His notoriety has everything to do with hip-hop, and his stake in the company has everything to do with his notoriety as a hip-hop artist.
Not according to Forbes[0] there aren't.