The late Tupac Shakur defined the fraze M.O.B to mean 'money of bitches', although this definition had a meaning of its own, what tupac actually ment when he said it was that he was now MOB related, i.e, a Member Of Bloods. The Bloods are a west LA street gang.
Therefore the fraze is actually a clever double meaning.
Some rappers still use the fraze 'MOB' to mean Tupacs defined meaning 'Money Over Bitches' without knowing what he was truly implying.
"I heard steve is now a M.O.B"
"Get rid of that girl, M.O.B"