Classifieds Website

I am looking to build a classified website that will allow customers to sell vehicles, real estate and five other small categories. There will also be places for advertisements. The website will be mostly Bilingual (Spanish-English) but I will provide the translations. Most of the specifications of the site are similar to what can be found across existing classifieds and listings sites. On the site there will be major categories and minor categories (ex. Real Estate is the major categories and for sale and for rent are the minor categories). So when someone clicks one of the major categories it will take them to a page where they can select from the minor. This will only be the case for real estate and vehicles. I will need the ability to charge for some postings and not for others. For the ones that cost I will need to be able to add features to the add that will cost more money such as bold text, featured add, and etc. Experienced developers/designers only please. The nature of the relationship should be considered long-term, as we will look to progressively improve the site and add additional features as the website evolves. Additional requirements will be given to serious bids.