If you aren't an attorney, I would be very very careful in doing this for your friend, as it may be construed as the unauthorized practice of law, which is a crime in the State of Washington. I suggest reading the information in the link I have provided below. I suggest that you be very careful here.
This advice is for INFORMATIONAL PURPOSES only and should not be relied upon as legal advice. No attorney-client relationship shall be formed as a result of the answer above.
It is one thing for the parties to formalize their agreement in writing, it is something else for a third person to do so as at least appears to be practicing law without a license, which can be criminally prosecuted. Your friend would be better served hiring an attorney, who know our state's laws regarding contracts, licensing and insurance issues, to draft up a contract that will be enforceable. It will save him headaches and money in the long run.