This isn't your first real estate project, is it? It seems to be very well thought out and from the screenshots it looks like it has everything they'll need.
Very well done, the site looks awesome!! Good luck with the business side of things. It can (and will) get tough, annoying, hellish, etc, but if you believe in your product and have set good, attainable goals (both long and short term), then it will be all worth it in the end, as long as you don't give up!
I've been toying around with developing an app strikingly similar (though far less featured) to what you have done.. I for one am very interested in hearing about the licensing/costs you are going with. I have a few clients who may be interested in such an app, feel free to pm/email if you don't wish to discuss in the open... (or if it's not suitable for the forum)
Here's a little background about the app, I decided high school was worth less, so I got a job. This parttime job turned into a pretty much fulltime job, I would go to school, then go to the job working for a real estate agency. The problem was, that while I was creating an app [very similar to this, however not as complex], the code got bloated, ugly, people were annoying to deal with. My boss and I decided to quit and start our own company. Using his knowledge of about 2 years in the business, his roommate who does webdev for some real estate firms on the side of his real job, and my php skills, we came up with this product.
The best part is that the code is unbelievably clean considering the vast nature of this project. There are deffinitely improvements to be made, but the framework is pretty rock solid.
I am going to probably release my database abstraction object framework under some sort of license in the future, its a great, convenient way to deal with the db backend, and it took nearly a year of thinking to develop.
Anyways, with fear that I'm going to be sent to enterprise, we are possibly going for $40/head-month. So, if a firm has 5 employees, they would pay $200/month. May seem like a lot, but if this software makes just one more $2,000 deal a month, its more than paid for.