Can you make $10,000 a month selling on Poshmark or Tradesy? ?

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You would need a steady supply of barely used high end brand and designer label clothes at very cheap prices and you would need to do nothing but sell clothes full time. You would require some type of inventory control system and enough space to operate a business. Because that's basically what this is: a business. 

The idea is that you buy big brand new clothes from thrift shops and "flip" them for a profit. Supposedly you can find near new big brand clothes for a few dollars and sell it for huge 200% markups. I don't know about thrift store where you live but if the brand is higher end than the Gap or H&M it's not in thrift shops. Mine don't have Chanel or Louis Vuitton. The big name stuff is skimmed out and sold through a silent auction book or sent elsewhere. So all that's left is old Navy and gap stuff.  And is anyone going to spend $30 on a gap sweatshirt they can get for $30 at the Gap?  And if you think you can get cheap on ebay- nope! Thousands are trying this idea and pushing the prices of used clothes through the roof. Lastly, people are smartening up when it comes to used clothing. They are cutting out the middleman and buying through thrift shops and  consignment shops directly

A few people maybe can make some money, but that window of opportunity for tens of thousands a month is closed. If you want to sell as a side hustle than give it a try, but there's very few who make those huge profits unless they do it as a dedicated small business.

no...................