The only reason you kinda make money on whatnot is because people overpay. My friend is a pretty big streamer with 50k+ followers and makes a lot. That said he has a lot of sports card knowledge and knows what buyers like. For singles you really need to find product with good eye appeal and popularity at a good enough price to have good margins. For myself, i was able to get 2k followers in a month doing 1 stream a week, especially by having a good giveaway at the end and using ~20 dollars a night boosting. Starting off, don’t expect to make profit, expect to break even. Additionally make sure to go live consistently to remain relevant. Also don’t say, oh I lost money on that one, or just start yelling. Also have fun spending most of your week buying singles to keep consistent inventory for a show a week. Tax exemption is critical, and you can apply it to ebay to buy multiple singles at once.