If you're unfamiliar with the concept of arbitrage, here's how it works. Wikipedia describes an arbitrage as effectively, "the practice of taking advantage of a price difference between two or more markets: striking a combination of matching deals that capitalize upon the imbalance, the profit being the difference between the market prices." Clothier was able to identify arbitrage opportunities in the grocery industry with precision.
Now you’ve got many different options to start earning online. If you saw something that really interests you, try it out and learn more about it. If you’re really wanting to make a full-time income online, you need to be dedicated to learning how to do what you want to do. There are tons of free resources out there. You just have to search for them!