The PIE project aims to provide Real Estate Investors with a FREE web based cashflow calculator to use to evaluate potential rental property income before investing. It is an Open Source project developed by Richard Bondi. Real Estate Investors can use the Demo application on this site.
Also, you can download a Working Copy to put on your site. This is ideal for Real Estate Investor's, Real Estate Agent's or Investors Club websites. The Source Code is also available for download to those who would like to customize the functionality.