Many years ago I attended a seminar on ethics in real estate sales where the attorney giving the seminar had the following to say on the subject:

"I'm going to tell you everything you need to know as a real estate agent about the subject of ethics as it relates to your relationship with your clients in the next 30 seconds. 

If you're wondering whether or not something you have knowledge of during a transaction needs to be disclosed to your client, ask yourself the following three questions:

1. Is this something that I believe could affect my client's decision to move forward with the transaction?

2. Is this something that I would want to know about if I were the client and thinking about moving forward with this transaction?

3. Could I convince a judge and jury afterwards that I truly acted in my client's best interest in choosing not to disclose this information to the client?

If you answer "Yes" to either of the first two questions, or "No" to the third question, it's definitely time to disclose the information to your client."