From a payroll board that I visit, the guru says:
"This is not my area of expertise, but according to my notes. - No FICA. - FIT is withheld unless a valid form 8233 is filed (each year). - IRS pubs 515 and 901 are supposed to discuss the federal rules. - I have no idea what the state and local rules are."
I would read the two IRS publications first before doing anything else!