Not sure about your state, but in Ca. you have to by qualified and bonded as an immigration consultant. Not just any notary can do these. Don't get yourself in trouble.
Under California law, the only individuals who can assist clients with completing immigration forms (such as the Form I-9) are licensed attorneys, individuals authorized under federal law to provide immigration services, and individuals qualified and bonded as an immigration consultant under California law (Business & Professions Code, Sections 22440, 22441).
A notary public who is not qualified and bonded as an immigration consultant is prohibited from completing immigration forms for his or her clients (Government Code, Section 8223 (c)).