It is highly recommended that a contract be drafted between yourself and your employer prior to starting the job. Contracts outline the terms of your employment including how many hours you are required to work, the tasks you are required to complete, and the amount you will be paid for your services. Without a contract, there is no legal way to prove your employment or hold an employer responsible for paying you once your work is complete. By signing a contract you are protecting yourself and your employer from any wrongdoing during your employment period.
However, do not just sign any contract that is given to you. All contracts should be read thoroughly and you should never sign anything with terms or conditions that you do not agree to. Contracts should be negotiated between you and your employer, not mandated or controlled by them alone. Before signing anything, be sure you understand what you are agreeing to. If need be, have a friend or family member review it as well to ensure there is nothing in it that seems suspicious.