Hi Margaret.  Not only is there a breach of ethics, but there may also be a breach of the law.  Unfortunately, very few consumers take any real action against estate agents.  I know that the regulating authorities are constantly overwhelmed with reports and complaints, but these are still represent the fraction that could/should be made.  The only way to retain any control is to ensure that nothing is signed at the start of the relationship, and even then the document you sign should be thoroughly examined first.