Where an owner of real estate has contracted to exchange it for property owned by another, whom a broker he employed has produced, the contract providing that the land should he conveyed by each to the other within twenty days by a good and sufficient warranty deed, such owner may recover from the customer the amount of the commissions paid to the broker, where such customer is unable to convey a good title to his property. Roche v. Smith, 176 Mass. 595, 58 N. E. 152; Volke v. Fish (N. J. Ch. '09), 72 A. 1011.