That would be retail arbitrage, one of the top careers for self-employed introverts. Practitioners of retail arbitrage buy products for pennies on the dollar at auctions, from online retailers, even at garage and yard sales, and then sell them online at sometimes-substantial markups. Fulfillment by Amazon (FBA) is the most popular platform for U.S. sellers, but other options work too. Learn the FBA ropes with this low-cost Udemy course.
Take it seriously. Yes, you’re applying for an online job. Yes, you can do the work in your underwear, but that doesn’t mean it’s not a “real job”. You must treat it as such or they aren’t going to treat you as a serious candidate. You aren’t the only one who wants to work in their underwear. In fact, the competition online is likely higher than it is in your local area.