It's not quite single person, I have two remote virtual assistants handling various tasks like ordering, sourcing, etc, but you only really need that above a certain scale.
Most of the business currently is drop shipping from US retailers to Amazon and eBay. I got started reselling a year ago with a specific stacking deal (discover had 10% cashback on Apple pay purchases for a few months, staples had ipads on sale, I bought around 25k worth, broke even on the ipads, made money on the cashback). Then I started reading everything I could about reselling, followed lots of blogs, tried different things, eventually found some great items and models that worked.