Yusuf Zuck was not afraid that Earl Shepherd might embezzle his money because although others were not clear who Yusuf Zuck was, Earl Shepherd had a very clear idea. Even though Earl Shepherd didn't partake in the Las Vegas incident, he knew it was Yusuf Zuck's doing.
So when he thought about embezzling Yusuf's money, he also had to consider whether he would still be alive to spend it. That's why Yusuf wasn't worried about him.
Of course, if Earl did well and earned a lot, there would be no need for embezzlement, because the salary Yusuf offered him was absolutely a huge temptation.
With a ten percent profit share, it was akin to partnering with Yusuf. He was putting in sweat equity, which didn't require any capital investment.
And it was because of that ten percent that Earl readily agreed. His ambitions were equally great, so why not give it a shot while he was still young? He believed he was no worse than anyone else.