Despite all the advancements in technology, billionaire investor Mark Cuban, 66, spends most of his day reading and responding to emails. Related: Mark Cuban Says 60 Is the New 40. "I have emails going back to the 90s," Cuban told BI. Mark Cuban. Related: Mark Cuban Compares AI Taking Jobs to When There Were 'Millions of Secretaries'Cuban's first entrepreneurial venture was MicroSolutions, a software reseller that sold PCs, software, and training to businesses.