Where plaintiff was authorized by the owner of land to sell it, and agreed to share the commission with defendant in case the latter found a purchaser, the contract was unilateral, binding on neither party until defendant found a purchaser. Wefel v. Stillman, 151 Ala. 249, 44 S. 203; Casey v. Richards, 101 P. 36 (Cal. App. '09); Painter v. Lamb, 65 Pa. Super Ct. 13; Pryor v. Scott, 200 S. W. 909, - Tex. Civ. App. -; Steinbrook v. Wilson, 190 P. 606, - Kan. Sup. -; Winslow v. Day, 183 N. Y. Sup. 2; Piper v. Allen, 219 S. W. 98, - Mo. App. -; John v. Thrower, 75 S. E. 819, 11 Ga. App. 494. See also Sec. 20.