In California, a broker must satisfy certain conditions to demonstrate entitlement to a commission when the seller is unable or unwilling to complete the sale. " 'It is well established, (1) in the absence of any specific agreement to the contrary, that a broker employed to sell real or personal property has earned his commission when, within the life of his contract, or any extension thereof, he has produced a person who is ready, willing, and able to purchase the property (2) on terms satisfactory to the seller, and has obtained a binding and valid contract for a sale on the terms proposed by the seller, or has brought the seller and buyer together and thus enabled them to enter into a contract of sale, or has produced such a purchaser who has verbally accepted the seller's terms and offered to enter into a written contract embodying the said terms and binding upon both parties. In such cases the broker's right to commission accrues when the contract of sale is executed, or when opportunity to make such contract is given the seller, and the broker becomes entitled to his commission even though the seller is unable or unwilling to complete the sale. ' " (R. J. Kuhl Corp. v. Sullivan (1993) 13 Cal.App.4th 1589, 1600, , quoting from Twogood v. Monnette (1923) 191 Cal. 103, 107.)