I am in Texas, actually Texas association of Realtors prepared such forms for all Texas Realtors. I believe CA association of Realtors has forms for CA realtors.
You do be able to pick one and use it. It is your own risk as most such forms are limited power. EX, if some one use my form in Texas without a Texas Realtor involved, it is un-enforceble.
Hire an agent or property or ask your attorney prepare one for you.