I would suggest pulling up a list of the newly licensed contractors in your area and marketing to them to establish a working relationship from their beginning. You could promote the services that you offer that will assist them in selling their homes and by signing up before they build, it will eliminate hassles for them.
You might also pull a list of the new home builders from your local permit office to see who's building.
Most established GC's eventually get their own realtor license if they specialize in new construction, so I'd suggest working on the new guys.