It is no mystery that real estate market is down, way down. Some Dual Real estate agents are trying to get creative by adding a yard sign but not listing the property on the MLS to other agents in the area. This gives a new meaning to exclusive listing. Why? Because a listing not on the MLS but has a Realtors yard sign gives the buyer no choice but to call the listing agent or the brokerage office only. Dirty Little Tricks of Dual Agency.