In spite of the reviews about Posh being on the side of the sellers, they are very harsh with sellers and issue warnings TO SELLERS when the CUSTOMER doesn't like the item or buys the wrong size (not sure how the seller can help that). They tell buyers no refunds or returns but have NO PROBLEM dashing off a return when any buyer of MINE wants one. I had to move mountains to return the WRONG ITEM and get a refund when it was my turn as a buyer.
Also note that you only get so much leeway - more than 3 complaints in 12 months and you are suspended. You have to ship in TWO DAYS (hard to do on a 3 day weekend with no post office. It can be done and you CAN make money but know going in it is no better than Ebay or Etsy and very little forgiveness depending on which end of the transaction you are on and the day of the week.
I'm not crazy about the whole socializing and parties and sharing thing. I'm not there to make friends, I'm there to shop and sell. There is also a large percentage taken from the sale so you may not make as much money as you would on say Ebay or Etsy. Unfortunately, (like Ebay these days) folks are encouraged to have "boutiques" of new item items usually factory wholesale items the sellers buy from China that are badly made of cheap materials. I'm also not a fan of stock photos (forbidden on Ebay) instead of a picture of the actual item I will be getting.
BUT...there are options to TRADE items (which Ebay forbids), you can "bundle" (put together bulk purchases) to save on the flat rate shipping and can make offers if you don't like the price. The small sellers on the site have better offerings (better brands, more selection, faster shipping, higher end) than on Ebay and Posh is formatted for those more comfortable with taking photos with their phone and texting (I'm not - I prefer to type on a PC to get the details).