A broker is required to use such skill as is ordinarily possessed and employed by persons of common capacity engaged in the same trade or business, and such diligence as persons of common prudence are accustomed to use about their own business affairs. Bronnenburg v. Rinker, 2 Ind. App. 391, 28 N. E. 568; Shepherd v. Field, 70 I11. 438; McFarland v. McClus, 1 Pa. Cases, 504, 5 Atl. 50; Mechem on Ag., Sec. 494.