The Buyer Agent will work for a buyer under contract. He or she can represent both buyers and sellers, but will only represent one client in any real estate transaction. The Single Agency Buyer Agent does not practice dual agency.
All legal obligations are to the seller.
If you are blindly calling on signs, attending open houses, calling and walking into real estate offices, you are selecting no representation and that agent is most likely a Seller's Agent. If you select buyer representation from an office that also lists homes for sale, you may end up with limited representation.