As someone with a background in Accounting/Economics/Finance etc. Im currently looking for ways to generate some passive income whilst being employed full time (9-5) ans hustling on a side online business (not yet finished).

So the question is, are there any legit websites or apps that one can use and generate some passive income? Any ways to get a small return over time? Investments, rewards, funds etc. General advice on how to make more money?

Goal is to maximize my minimum-average salary.