Now that he's been busted, it's pretty obvious what he's been doing all these years.
He had probably been a bookie for guys like Michelson and other high-profile, famous people who wanted to place a bet on some game. Instead of having to go to Vegas to make the bet, they just give Billy a call. He probably set the line and handled the whole thing. Over time, guys like Michelson ended up owing him a lot of money. So Billy gave Phil an insider trading tip with the idea that Phil will make enough money from the tip to pay him back.
He had probably been a bookie for guys like Michelson and other high-profile, famous people who wanted to place a bet on some game. Instead of having to go to Vegas to make the bet, they just give Billy a call. He probably set the line and handled the whole thing. Over time, guys like Michelson ended up owing him a lot of money. So Billy gave Phil an insider trading tip with the idea that Phil will make enough money from the tip to pay him back.