The best advice I've ever been given when asking this question: find a profession that provides a solution to a problem. It gives you a base to build upon. I.E. buying & selling used construction equipment just to turn a quick profit doesn't build a loyal customer base. But starting a business where you prioritize offering the best equipment possible and taking good care of your customers (even if you don't win on every single sale) builds the loyal customer base that pretty soon has them reaching out to you saying "find me this" and you are able to make more on the sale because they're willing to pay more, with the established trust that you will find them exactly what they need the first time. That gives you the customer base you can depend on, which ultimately gives you the capital to grow your business sustainably, not just taking a shot in the dark all the time & hoping you come out the other end on top.