You can pay a lawyer to draw up this agreement if you are a large company that has a big enough budget to cover the costs, but this is not necessary as you can do it for yourself. You can of course write out your own agreement using one of the many different templates that are available for download online. Both of these documents are completely binding in a court of law, the difference is the amount of money you are going to have to spend. Each of them must be signed by both parties and in many states notarized in order for them to be legally binding.
Ownership Issues upon Death of a Partner_ A clearly established process of endorsement of ownership, role, and responsibility should be included in the agreement should one of the partners become incapacitated or dies.