Unless you sign a Buyer's Agency Agreement, you are not obligated to stay with any agent.
However, if you use two different agents to see the same property, than the agents may end up fighting over the commission due to which agent was the "procuring cause" for you finding and buying that house. Personally, I don't really like showing buyers a house they saw with someone else because it gets sticky. Just make sure you would switch agents with cause and it shouldn't be a problem for anyone involved.
Brian P. Sears, Broker/Owner
Sears Real Estate... more