Build a Multi Vendor Marketplace with Tier Memberships

We are creating a site where users can create their own comic book store. In this site users will be able to upload inventory, create store logo and storefront image, and browse other users stores. All users must be registered, but there will be both a paid and free membership. The free membership with allow users to still create a store and list within it, but the premium membership will unlock access to certain features on the site such as discounts on premium ads, unlimited listing, prime search results placement, and discounts on ad space (we will sell ad space on our site so that users can advertise their storefront.) Currently I am creating a search function that searches all the comic book stores on the internet for comic books. This site will feature a "get inventory" tool where you can search for more comic books to include in your store. Free members will have access to a internal search within the marketplace, while premium/or paid members will be able to use the special external search feature. The home page will be a splash login page with the company logo and "login" or "register (it's free)" Below the two options will be a simple about section that highlights the feature of the website. While listing will be free, there will be a small final value fee (%) charged for sales completed within the marketplace. While unregistered users will be able to search through the site for comics, they will not be able to make a purchase without a membership (free or paid). All new users will be able to enjoy a free "premium" membership on a 30 day trial basis, after which will be required to either purchase the premium features, or downgrade to the free basic membership. Images for logo, and background will be provided, and our team has a strong design sense, but lack of technical knowledge. The "search" we are working on will be complete by the end of April, and we would like this site to be completed by then as well.