Final answer:
The act of splitting or sharing the commission with a prospective client in real estate and insurance transactions is called a Commission rebate, a strategy used by agents to attract clients.
Step-by-step explanation:
In the context of real estate and insurance, the practice of splitting or sharing a commission with a prospective client is known as a Commission rebate. This happens when an agent returns a portion of the commission paid to them to the client or customer. This can be a selling point for agents looking to attract clients by effectively reducing the overall cost of the services. The other options listed, such as Commission collusion, Commission negotiation, and Commission sharing, have distinct meanings and do not accurately describe the concept of an agent providing a rebate of their commission to a client.