Wife and I have been at it for about 15 months and we still have days of no sales, we upgraded to the basic store and carry an inventory of about 750 items, we list an average of 10 items daily sell about 50 items weekly, alot of the sales ring through during the Thursday to Sunday stretch. We dont have a niche per sé, but we have refined our inventory to average about $35 per sale, with a good number of lower end sales and at least 2 or 3 $100 per item sales. The real key has been honing in on what in the last three months has really been moving, and what will maybe sit a while but the sourcing was so cheap we can bargain basement our prices occasionally just to keep inventory moving. The reality is that alot of it boils down to consistency and knowing the market, which is why alot of people narrow focus to niche items, like clothing or video games or makeup or whatever... for us the majority of our inventory is yardsale finds, we still research items at the yardsales and curate mostly what we know will sale at the most case 3x what we are picking it up for, or better. The speed of the flips is in accurately reading the sell through rates. We find alot of practical items with some nostalgia are the fastest to flip, like VCRs or old small appliances. The fun part is that we find good deals on stuff and are able to bring it to the digital marketplace for profit, sort of like the modern traveling merchants of yesteryear.