it depends on your skills.
Crypto currency trading / investing is one good example
You can earn for your content on services like steem with very little to no upfront investment
If you have specific skills and good communications you can earn on freelance websites like upwork.
you can start your online business by having an eCommerce store online.
these are just a few things i can think of on the top of my head. feel free to add to the list in comments
