Although an agreement signed by a real estate owner to pay an agent a certain commission in the event that the owner shall make a sale is a unilateral contract, and invalid on its face, yet where the agent goes to the expense of advertising and endeavoring to sell, this is a sufficient partial performance to render it enforceable. Lapham v. Flint, 86 Minn. 376, 90 N. W. 780; Schoenman v. Whitt, 136 Wis. 332, 117 N. W. 851; Hanlon v. Dunne, 189 I11. App. 123.

Where defendant was authorized by the owner of land to sell it and agreed to share the commissions with the plaintiff, in case the latter found a purchaser, the contract was unilateral, and binding on neither party until the plaintiff found a purchaser. Wefel v. Stillman, 151 Ala. 249, 44 S. 203. See also Sec. 397.

A contract by the owner to pay another a commission on a sale of property, whether effected by the owner or agent, is a unilateral contract, and where the owner unaided in any way by the agent, effects a sale, the agent can not recover commissions; but if the agent effects the sale his commissions are recoverable. Taylor v. Barbour, 90 Miss. 885, 44 S. 988; Humphries & J. v. Smith, 5 Ga. App. 340, 63 S. E. 248.

Where a contract employing a broker to sell coal lands provided for the payment of a commission on the broker effecting a sale within six months from August 19, 1904, and further provided that if, during the six months, the broker named to the owner a probable purchaser, and the property came under the control of the person so named, the broker should be entitled to a commission if a sale or lease was made within a year from Feb. 10, 1905, the agreement was neither unilateral nor abnormal. Langdon v. Taylor, 180 F. 385, 103 C. C. A. 531.

Where a property owner states to a real estate agent he will purchase at a specified price property held for sale by the latter, if the latter will procure a sale of the former's property, there is an offer, in the nature of a continuing offer on such property on the owner's part, and, if not previously withdrawn, the agent furnishes the consideration by rendering services resulting in the sale of the owner's property, there comes into existence a unilateral contract executed on the agent's part, and binding the owner to purchase the property held by the agent. Carroll v. Goldstein, 211 I11. App. 315.