You've received some really great and correct answers here.
An agent is not only someone who just physically shows you homes, this person actually will REPRESENT you in the home showing process, the offer preparation and submission process, the negotiation process, etc. An "agent" has a fiduciary responsibility to protect you (the client) and look out for your best interests. An actual agreement should exist between client and agent, but as the answers below indicate, it would be a kind courtesy to only incorporate someone and use their time if you DO actually want to engage them as your AGENT for your purchase or sale. Agents do not get paid until a client buys or sells something, so unfortunately most of the time, agents end up doing a LOT of work for free when clients just "vanish" or are otherwise not seriously shopping or looking. I realize that may sound harsh and that is not the intention at all. Think of it like this, agents sometimes work for days/weeks, maybe even months with a client before finding "just the right home". That agent is workign without pay all that time, until that client purchases a home and it closes at the title company. Your agent really wants to do a great job for you! But, any and every agent deserves the same loyalty from the client as what they deliver to the client.
YOU, the buyer, the client choose your lender. However, your agent most likely has some recommendations. The reason for this is that your agent sees these types of transactions and processes EVERY day and probably by now has a pretty good idea of which lenders and/or mortgage brokers or mortgage professionals work the best for their clients. You are not obligated to use the services of anyone whom your agent refers, but you may want to consider that your agent does this stuff EVERY day, and may have some truly great suggestions and/or recommendations.
Your agent wants what is best for you. Just be sure you're working with an agent whom you trust and feel confident using. If for some reason you do not want to actually work with or hire a person you've been seeing homes with or communicating with, I promise you, that person would appreciate knowing #1. how they can better meet your needs, or #2. if you do intend to actually buy with them or not, #3. if you're not pleased with their service let them know, allow them to fix it or let that person know you're moving on.
In YOUR job you have to manage your time and prioritize based urgency and seriousness and you can not work for free--- your agent must do the same thing. We all must.
Give your agent a chance. If that person has been working diligently for you, they most likely really truly want to do a great job for you. If they do not, kindly say "goodbye" but let them know.
Best of luck to you in your search and endeavors.