Final answer:
The type of agency that might exist before a listing contract is signed is Agency by estoppel. It comes into effect when the actions of the seller and broker imply an agency relationship, even without a formal agreement. The term Agency by estoppel is crucial in this context, whereas Express agency refers to an explicitly stated agreement.
Step-by-step explanation:
The type of agency that may exist before a listing contract is signed between a broker and seller is Agency by estoppel. This occurs when the actions of the parties imply that an agency relationship has been established, even though there is no formal agreement. For example, if a broker starts performing tasks on behalf of the seller like advertising or giving advice on pricing, and the seller allows this without a formal agreement, a third party might reasonably assume an agency relationship exists based on these actions. Therefore, the seller might be estopped or legally prevented from denying such an agency relationship if the broker's actions were taken with the seller's knowledge and apparent consent.
It's different from Express agency which is created by an explicit written or oral agreement. Partial agency and Substantial agency are not recognized terms in this context.