Under what condition can a broker place a lien on real property for unpaid commission?

A broker can place a lien on real property for unpaid commission when there is a contractual agreement in place. This is because a real estate broker has the right to assert a lien based on the terms outlined within a listing agreement or other contractual documents that establish the obligations of the parties involved. Such agreements typically specify the broker's entitlement to receive compensation for services rendered, and this legal backing is crucial for the broker to initiate a lien claim.

The other options do not provide the necessary basis for a lien. While a judge's approval might be required in certain legal contexts, the fundamental reason a broker can place a lien is due to the existing contract that stipulates the commission. Likewise, while property type (commercial vs. residential) might influence different aspects of real estate law, it does not inherently grant a broker the right to place a lien without a contract. Additionally, simply having payment overdue by 30 days does not automatically grant lien rights; the existence of an enforceable contract that explicitly contains lien provisions is what enables that action.