Where a contract between the owner of property and a broker who undertook to bring about an exchange for certain other property, provided that such property should have an annual net rental of a specified sum, it meant that it should yield that amount above all liabilities to the owner, such as taxes, assessments, etc. McVicker, etc., Realty Co. v. Garth, 97 N. Y. S. 640, 111 App. Div. 294.