What is the ruling on someone who learned about a property for sale through a sign placed by a real estate office, then bypassed the office and directly contacted the property owner or acted as an intermediary in its sale? And does the office deserve anything?

If the property owner agrees to sell his property through someone he knows, that person is entitled to a brokerage fee, and the office owner is not entitled to anything because the sale did not occur through him. Brokerage is a permissible contract, and the property owner may terminate the agreement with the office owner at any time. If the contract is terminated after the office owner has commenced brokerage activities, the office owner is entitled to a fee equivalent to the customary wage from the property owner, because he began the work and the termination was initiated by the owner.