Shortly after its passage the validity of the statute was sustained against a constitutional attack on the ground of class legislation and the interference with the right of contract. In the case of sales of real property, only contracts between an agent or broker and an owner are covered by the statute. An "owner" includes one whose title is only equitable or a broker who is also an owner, but excludes one who merely has an option to buy land. The statute has been construed to cover only contracts to pay a commission. The test of what constitutes a commission seems to be not the nature or manner of payment but whether the services for which the payment is made are such as to be within the category of "brokerage contracts." The statute, of course, applies to "selling," "purchasing," and exchanges of real estate.
Lisle R. Guernsey,
The Real Estate Broker's Statute in Washington,
23 Wash. L. Rev. & St. B.J.
Available at: https://digitalcommons.law.uw.edu/wlr/vol23/iss2/3