Zimmerman, a real estate salesman, asked Robertson if she was interested in selling her property. Robertson said she might be. Zimmerman came to Robertson with an offer by Velten to buy the property. After some negotiations, both sides signed a contract for sale. Zimmerman told Robertson he was being paid a commission by Velten. Before the deal on the property was to close, Robertson asked for a copy of the agreement between Zimmerman and Velten, but they refused. Robertson refused to go through with the deal. Velten sued, claiming there was a valid contract. Robertson said that Zimmerman violated his fiduciary duty to her to disclose his interests. Is the deal valid? [Velten v. Robertson, 671 P.2d 1011, Ct. App., Colo. (1983)]