ADT, one of the proposals that I put together for one of my clients who was trying to do the same thing on the residential side, ie. broker, homelender, handyman, movers was to recommend that they spend a little bit of money to do two things:

-put down a formal agreement as to how they would work together
-develop a website for all of them to present a full service solution to the client

This takes work and you can run into obsticles but I am sure no one else is doing it!