Country Specific Property Listing Site

I need a property listing website. I am open to any language/database for this, php, asp.net or possibly a modified open source script. The Programmer will already have done several real estate / property listing sites and should be able to modify an exisiting script to adapt it for the market. The solution has to be properly tested and any browser compliant and the listings will need to be optimized for the search engines, no payment gateway required at this time. I will provide a more detailed spec and links to a couple of sites I like to bidders who have established they have done projects like this already. I will respond to bidders based on the quality of sites they have completed previously.