ThredUp is a service that pays you for clothes that you send in through the mail. You order one of these free bags, then send it back with shipping already paid for. They select the clothes they’ll accept and pay you some fraction of their sale price, before listing it on their site to purchase. The clothes they decide not to resell get recycled. I really like this model because I end up donating most of the clothes I don’t want anyway, so getting paid for any items is just a bonus for me. Because I don’t have to pay for shipping, the service doesn’t cost me anything which is the reason I use it. Overall it’s a very smart model, since the markup of the items on the site definitely covers the cost of shipping the bag, and the small payments incentivize people to send in more clothing. Genius.