I have had this question come up a great deal in trying to find enough income to quit my full time job. Mind you, it wasn't the smartest thing to do and I really don't recommend it to anyone but I have the safety net of another income. I routinely use the BBB and I Google the business and look for reviews. I also go to Glassdoor, which are reviews by current or previous employees. That helps me decide if I want to pursue a relationship with that particular company. If it's an app, I also utilize the read more button so you can read all the reviews, which most negative reviews are buried in that spot. There are many scams out there and I have been the victim of a few many, many years ago which has made me so much more skeptical and careful.