Business Networking Website Design Prototype

I am seeking a developer to design a prototype for business networking website. Must have experience developing networking sites (please provide examples). Must have experience working in startup companies and defining technical specifications. Scope of project may expand as prototype evolves. I would like a detailed quote that gives me break down of all costing for the project and fully detailed of what you are proposing to offer. This will be a fixed cost project. Some of the functionality that we are looking for: User Profiles (e.g., Registration and Maintenance and Notifications, etc.) Media Content Management (e.g., RSS feeds, Videos, Pictures) Pagelets and Dashboards (e.g., Widgets) Some collective/business intelligence prototypes (e.g., SPSS, SAS, etc.) Skills we are looking for: - The final product will be housed and managed within a Mac environment. - Website & Content management security access. - Website prototype presentation experience with recent examples