A lot of debate has occurred in recent years about whether it is more beneficial for SEO to have your IDX solution integrated via a Subdomain, like IDX Broker provides, or in a Subdirectory of your website. Google has settled this debate with a definitive answer: It's a TIE!
Subdirectory Integration: YourWebsite.com/Subdirectory
IDX Broker Custom Subdomain Integration: Subdomain.YourWebsite.com
IDX Broker has offered integration via Custom Subdomain as an additional feature since our launch. Subdomains are the most efficient way of incorporating your IDX data, since you can manage it separately from your website and host your primary website and email anywhere you want. Most importantly, the Custom Subdomain enables the display of your IDX tools on a subdomain of your own website and gives your root domain all the credit for indexed IDX pages.
For a complete Roadmap of all SEO features offered by IDX Broker, see this article about SEO.
Here is a blog post for more in-depth information.
For specific instructions, visit this article on setting up a Custom Subdomain for your account.
If you already have a Custom Subdomain set up, don't forget the final step to ensure proper indexing and verify the ownership of your subdomain with google.