Consulting arrangements are the ones most often documented by email and a rate. That works until something needs to be enforced: an unpaid invoice, a scope that expanded without anyone agreeing it, or a question about who owns what was produced.

Ownership is the term most commonly missing and the most costly to omit. Work created by an independent contractor generally belongs to the contractor unless it has been assigned in writing. A business that commissioned work and paid for it can discover during diligence that it does not hold the rights, and the fix requires a signature from someone who no longer has any reason to give one.

The other terms do ordinary but necessary work. What is in scope and how changes to it are agreed. When payment is due and what happens when it is not made. What confidential material may be used for. Whether either side may work for competitors, and under what terms and conditions. How the arrangement ends and what happens to any work in process or completed work product.

Whether a person is properly classified as a contractor rather than an employee is a separate legal question with its own consequences, and it is worth confirming rather than assuming.