I haven't heard of this, but it's a very interesting concept.
If done right, this would be mutually beneficial and could be a form of community service that we're providing.
I can see where it might be somewhat controversial though. It would take some real thought to make sure the message isn't perceived as taking advantage of the less fortunate and doesn't reflect poorly on your company image i.e. dirty, slovenly dressed Page Ranking representative becomes the face of your company. Yet if the "opportunity" for emloyment that you open up to the homeless is what's conveyed, this could be very positive.
Maybe even add a tag a the botton of the sign stating that "$300 from every closed loan goes to support the homeless" or something.
Someone should test market this and let us know how it goes.