Personally when I was involved in the life extorting drug dealers was the easiest and most lucrative. It's a dirty business, they can't avoid it or complain unless they were protected and if the law approached me about it I knew they were a snitch. Would also rob one and sell stuff to another for a discount to keep them happy. Loansharking is good but you have to use violence and sometimes it's on people who don't have any reason not to go to the law. Another good one is union jobs at a convention center. The companies charge an extra fee to get your goods delivered early or taken down first. If you get a fork lift driver to put a clients stuff in a place thats easy to get too you can make a deal with the client for less than the company would charge. Works every time.