We require a Joomla expert. If you don't have Joomla experience, this is not the project to start with.
There are several free shopping cart solutions available for Joomla. Part of your job would be to choose the best solution and integrate it into our site.
Our site will provide subscription based access to our Realtor database. Depending on the users search criteria, a data-set is established and a subscription price is determined.
We have an example site to model this functionality.
We require this to be developed as a Joomla module or component that can easily be installed and adapted to other Joomla sites and applications.