Coding a listings site

General information for the website: Car wesbite like autotrader
Kind of development: New website from scratch
Description of every page/module: i have a full set of PSDs that need coding. the website will be similar to autotrader.co.uk but ultimatley it is a simple listings site.

users will be able to add a maximum of 2 listings at any one time for free and have an option to pay to have more (all payments via paypal which you need to integrate).

we also need a sub admin for "dealers" where they can add unlimited listings and each listing will have their logos and contact details

the Admin will be able to enable and disable the sub admin accounts (for non payment) but the sub admin do not have the ooption to pay via paypal.

will need to have a special lisitngs (think eBay Google ads style) for the sub admin listings above the normal users listings

needs to be programmed to be responsive fully W3C and seo optimised.
Description of requirements/features: listings pay options for extras and paypal integration for normal users to purchase extras
CMS and Admin requirements: full admin with integrated analytics for admin and sub admin
Similar urls: autotrader.co.uk
Extra notes: