Need a full service property information website and portal.

As an information service portal, the site will:
- have dynamic content with users able to create & update content, blogs, discussion forums, groups, etc in real-time
- be able to crawl other sites for property news, data, etc; as well as generate its own data, tools and information resources all arranged in a pre-defined logic
- email and phone alert service to members (e.g. property price change alerts, etc)
- store database of users details and property requirements, scaleable to take up to a million users
- Auto distribute newsletters and other information to users on the database

As a property portal, it should
- Take on up to a million property listings, picture uploads, etc
- Users should be able to search by any free text, location (full or partial postcode, city, town, country, address, price, rental yield, number of rooms, type of property, proximity to places of interest (e.g. stations, schools, etc), other property features, etc
- Ability to search multiple locations at once. separated by a comma or check box option
- Fully integrated with google maps and other popular maps
- Ability to create sub-domain websites & accounts for partner agents (up to 1000) who can add, manage, edit their own listings all visible on the main web domain


Other Requirements
- Fully search engine optimized with the goal of ranking top 10 on all major search engines using defined keywords
- Ability to host advertisement banners for sale to other businesses and display google ads on unsold banners

Unable to find another site online that has all of these features but sites like http://www.propertyportal.com/ or http://www.globrix.com/ are close to what I'm describing

Happy to do the project in phases so feel free to provide a phased quote or for the complete project with an indication of timelines