[header] How to write a business contract [title] Determine if all parties are legally able to participate. [step] The contract will not be valid unless everyone entering into the contract is fully able to understand what they are signing. To facilitate this understanding, everyone involved should meet the following requirements : [substeps] In almost all cases, a contract is not legally valid unless the parties involved are at least 18 years of age. 
Look up the laws in your state or locality if you think your case might be an exception. As an exception to the above rule, most states allow emancipated minors to enter into binding contracts.