Establish ownership rights to the work. Even in service situations, a product is sometimes the result of the work, so you should also include which party retains ownership rights. For example, the copywriter can state that she turns over all rights to the writing of the brochure to the customer and that she makes no claims of ownership to the writing once the customer pays for the written product. Add signature and date lines. Be sure to provide a space for each party to sign and date.
In legal terms, a contract is any agreement between parties to exchange things of value, such as goods and services for cash. A simple handshake agreement is legally binding, but its terms are not always provable if a dispute arises. However, you don't necessarily need pages upon pages of legalese. A basic contract agreement often works best for a simple business transaction.