A complaint which alleged that complainants were real estate brokers and that defendant, well knowing the fact, gave them an option on his property and agreed to pay a commission for their services in case of a sale, and that they procured a purchaser, and in pursuance of negotiations initiated by them a sale was effected, stated a cause of action on the theory that the plaintiffs were brokers, and hence they could not recover on proof that they were mere middlemen. Southack v. Lane, 65 N. Y. S. 629, 32 M. 141; Walker v. Osgood, 98 Mass. 348.