customized E-Commerce

HI there I need some customization to my E-commerce site, which makes it valid that anyone can make an accout and start adding their own products to the site, with all its manners... By uploading files, with their photos too, a set of information and specifications to be specified during the upload process, including prices, description, etc... But each product added by users should be approved by the administrator before starting to show up on the site Regards