When choosing an agent you will be asked to sign an agreement stating that "Agency" has been explained prior to viewing properties or submitting an offer to purchase. If an offer is presented without a written agency agreement then the agent can no longer represent the buyer.
Sometimes you may be hesitant to sign an agency agreement when the process is new to you and the agent was a stranger up until a moment ago. This can be resolved by signing a short term agreement where your interest are protected but you can also get to know each other before signing for a longer period.
Still have a question, e-mail me at firstname.lastname@example.org.