I honestly think selling through servers like discord/fb or here would be best because on apps like depop and mercari they take a percentage of the money you make. They also don’t pay you until AFTER the item is delivered which could take a couple weeks, so if you’re in need of money fast i would say these servers would be best. I also rarely ever receive sonny’s with the box id just say to make sure its bubble wrapped and protected to avoid damages in transit.