Where a broker is engaged to procure a purchaser for defendant's premises, and defendant enters into mutual contract with the purchaser so procured, the broker's commission is earned, as a general rule, but where the commission is agreed upon, on the theory that the deal shall go through, and it does not, through no fault of the principal, or where the deal is not consummated because of fraud or misrepresentation of material facts by the broker to his principal, the latter does not become liable because of his acceptance of the purchaser. Marks v. Schultze, 177 I11. App. 638.