A principal is under certain obligations to his agent and to third parties. He is under obligation to pay the agent his compensation. The amount of the compensation or salary may be stated in the contract or it may be based on the reasonable value of the services rendered. Unless it is otherwise agreed, an agent will not be entitled to compensation until he performs what he has agreed to do. He is entitled to be reimbursed for any money he may have advanced for his principal. A principal's liability to third parties includes his obligation to perform all contracts made by his agent within the scope of the agent's authority. A bank cashier is an agent of his bank and has power to draw checks or drafts upon the funds of the bank; to indorse and transfer negotiable paper (checks, bills, notes); to certify checks drawn by depositors; to collect money due the bank; to borrow money for the bank and to loan money. Sometimes when an agent deals with a third person he may not tell the latter he is acting for a principal. An agent is always liable in such a case.