Is it ethical to contact a few brokers for them to know that I am looking for an investment property?

Yes. Most brokers wont waste their time looking though if they know you are working with multiple brokers.

yes

While it is not illegal to contact multiple brokers, it is much more productive and cost effective to work with only one. Your broker should be an extension of yourself and becomes your eyes, ears, and legs in the market. If your broker is not providing professional or satisfactory services, find another broker and give them your undivided support.

Most people don't understand the amount of work it takes to find good properties for a buyer. If you are working with multiple brokers you are really doing a diservice to the group in that all they have is their time. Only one may get a deal and the others make nothing for their efforts. When you use up someones time, time that could be spent working on something that will result in a paycheck, the hurt goes beyond the person to their family without an end result. Other professions don't work that way and no one expects them to. You certainly wouldn't get a group of lawyers all to draw up a contract you need, you pick the one you like the best and let the others go unpaid for their work? Find a good broker that will work hard for you and in your best interest. But have some loyalty. In the long run you will be the winner.

Absolutely. However, it is best that you do not mislead anyone throughout the process. Most brokers won't give you the time of day if they know you are working with someone else. So, be prepared to pick the one who you have the best chemsitry with, who appears to be knowledgeable and the one who is willing to give you their time and efforts to find the right property for you. It is likely you already know who that broker is.