The article mentions it. He started doing the arb with $50k of his own money through a bank account another Effective Altruist in Japan helped him set up, then:
> With SBF’s initial $50,000 compounding at 10 percent each day, the next step was to increase the amount of capital. At the time, the total daily volume of crypto trading was on the order of a billion dollars. Figuring he wanted to capture 5 percent of that, SBF went looking for a $50 million loan. Again, he reached out to the EA community. Jaan Tallinn, the cofounder of Skype, put up a good chunk of that initial $50 million.
