Not all wall street firms end up success, many were bankrupt, but you won't hear the bankrupt story. The higher the leverage, the higher the bankruptcy risk. And for sure, real estate business has the highest leverage across industries IIRC. What I want to say is, you don't always need leverage. You can be wealthy from side hustle without borrowing any money. The key is reinvesting your excess income, not from debt.
But what if the income that you have monthly is not even enough for your family's daily needs and you want to invest in order to gain more income? The only way is to borrow but you should use or invest it wisely. Knowledge is very important and your strategy to gain profit.