@Joel, Yes your Wordpress site can be branded, designed, developed and hosted on a php platform, anyway you wish. It's only if you hit the bigtime choose managed hosting solution like Wordpress-VIP, that you will have additional Wordpress branding required.
Wordpress is one of the best open source CMS solutions out there. Chock full of free plug-ins so a non-developer can get a lot of common functionality right out of the box.
However, if you want custom functionality; functionality that is out side the norm of most websites, then Wordpress is tougher to develop in than the more recent frameworks. For example, there are CMS solutions like Wordpress that are built in Rails, Django, and even Node.js. Those are much more easy to extend with unique functionality, because it's built in an MVC framework.
With Wordpress you have a great free open source CMS because of how long it has been around. However, with thesis and many other Wordpress theme frameworks, adding functionality out of the norm may take longer and cost more.
Wordpress is the probably the way to go if your website is pretty straight forward. Most investor, agent and broker websites seem to be. If that's the case it's probable that Wordpress already has every plug-in built that you need.