Need suggestions for new referral site

[webauthor]

We have a customer who is wanting to start a referral company similar to 1-800-dentists.com -

We definitely will use WP and a StudioPress theme for the front end. We were curious however is anyone could recommend a way to handle the back end.

The flow is pretty simple..

John Doe is looking for a coach. He visits the site and types in a Zip code, the site would then display all the coaches who have paid to be listed in the referral site.

On the back end, Coach Mike would like to part of the referral service and gladly pay to be listed on a search result. Once Coach Mike subscribes he could edit his listing information. There is obviously a lot more but those are the basics. Has anyone come across a referral type plugin that would do the job? Perhaps a membership plugin that has the ability to search and display listings based on several factors...

Any suggestions would be greatly appreciated.

Thanks,

John