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.
Describe the payment terms for the transaction, including the total amount for the service, how much and when the deposit is due and how much and when the final payment is due. Spell out a time line or milestones. Include specific dates for the delivery of parts of the service or the final deadline for the service to be complete.