Final answer:
Placing a "For Sale" sign by Action Realty without a written agreement is the incorrect action, as real estate agreements must be written to be enforceable.
Step-by-step explanation:
The incorrect action in the scenario where an owner agreed by phone to allow Action Realty to sell the owner's vacant lot, and the broker sent a salesperson to place a "For Sale" sign on the property, would be placing the sign without a written agreement. Real estate transactions and broker agreements need to be in writing to be enforceable due to the Statute of Frauds. Since the agreement was made over the phone and there was no mention of a written contract being signed, placing the sign without this could be considered an unprofessional and potentially illegal action.
Real estate transactions can often present limited truths, such as advertisements that fail to disclose negative aspects of a property, like a landfill next door or a factory across the street. These omissions can sometimes be inferred from a low selling price or confirmed by visiting the property in person. However, ethical standards in real estate require full disclosure of material facts that can affect a property's value or desirability.