ThredUP sends you a free Clean Out Kit to fill with all the gently used, on-trend clothes you no longer wear. They'll take care of everything else, including professionally photographing your items and listing them on the site. You receive an upfront payout once the items are processed, or if it's a unique item, you'll be paid once it's sold. Payouts are offered in the form of ThredUP store credit or donation to a cause, or you can transfer the cash to PayPal.
How much will you make? I think my best month with Google AdSense was almost $5,000 over the last ten years. That amazing month blew my mind since it was actually near the beginning of my blogging journey. When you go from making zero to $5,000 in a month, that will rock your world. For me, it also got me even more excited because I knew there were other ways to monetize.