September 2014 - last edited September 2014
if you have the ambitions expansion pack a consignment shop comes with that pack you then via edit town place the shop in game your self then send a sim to consign items to sell from the sims inventory the clerk will if the goods sell you'll get a pop up message and the money put into the family funds
i'm not sure exactley what you can consign i know nectar can be consigned to sell, as i usually just drag and drop from the inventory to sell items
edit had a quick search carl has a guide here if you want to bookmark it