An advertising agency retainer agreement is a contract by which a client guarantees work to an agency for a specific rate and amount of time. In this type of agreement, it is also common for the client to pay the agency an immediate advance in the form of a retainer fee. The agency benefits from the drafting and execution of an agreement because they are given a guaranteed income source. However, there are also benefits to the client, including consistent monthly marketing costs, increased familiarity with the agency, and the ability to craft long-term goals with the agency. The agreement becomes legally binding once it has been signed by both parties.