It’s typically not required, so it’s usually your choice.  Ask any mediator you are considering working with if he or she requires this (I don’t, and instead let clients choose whether or not they need them).  If your mediator is also an attorney, he or she can help both of you understand the law, what a court might do in situations like yours, and draft your legal agreement and related court documents.  If you like, you can also have an outside attorney of your own coach/advice you individually, read through and provide you with individual feedback on the legal documents before you sign them, draft your legal agreement and related court documents, or work with you in any other way you find helpful.  For clients who wish to work with outside professionals, I typically offer referrals so they can find someone best suited to meet their needs.