When you have a business where customers contract you to perform a service, you need a legally binding agreement to spell out of the terms and conditions of the business relationship. According to "All Business," a business agreement serves as a guide that all parties to the agreement must follow. Generally, one party draws up the agreement and both parties sign the it as an acknowledgment of the terms and conditions it contains.
You may want to have an attorney review and make suggestions on a template of your business contract. An attorney can pinpoint issues for your particular business that you may need to include in the agreement. You can use a business agreement template and modify it to fit your needs, rather than writing the agreement from scratch.