The good thing you can become a billionaire at any age and any subject. The list proves it. The first one was in Computers, Bill Gates. The other in the hardest to make money but he is second with a great system in the stock market field is Warren Buffet. Trump way done in the list did it with Real Estate and gambling etc. If someone has the time give us a list of the ways that they became billionaires that would be very intereting. I only know these few.