No matter what regular job he got in the past, in his mind, he always been a professional gambler - pool, gin rummy, poker, blackjack, roulette, golf, horses, whatever... But it all changed when in 1982, he moved to Vegas and focused all his efforts into being a professional gambler. After being broke fifteen times, as he said, he started to focus, went on a 30-year winning streak as a sports bettor, and became a success story.
In a good year, he can rake $15 millions from gambling, which account for only 20% of his revenues. So if $15 millions represents 20% of his yearly revenue. We can conclude that he rake $75 millions a year, most of it via real estate. Not bad for a degenarate gambler!