If you have an agent representing you, standard protocol is that should have been disclosed that to the listing agent prior to your viewing of the property. Bringing in another agent after the fact will open a can of worms.
As an example, does your agent expect to be paid a fee, and if so who would be paying that fee? The agent that showed you the property is probably assuming they will be the "selling" agent whether they represent you or not. Especially if the agent that showed you the house is not the actual listing agent. Even if it was the actual listing agent that showed you the house, they are assuming they will be credited with bringing you in as a buyer.
Bringing in a buyers agent after the fact can cause you to lose the deal too. If it is important to you to bring in your buyers agent after the fact then by all means do so, but be prepared, you may be paying your buyers agent their fee on top of all the other closing costs you will incur.
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665