But, if student gets accepted, defers enrollment and moves to California, and works full time, opens bank account in CA, gets Driver's license in CA, gets a new CA license plate for car and parents stop claiming the student as dependent for tax purposes, then your son becomes financially independent, and after living in CA for at least one full year plus a day preceding the residence determination date, he can claim CA residency.
Every student from out of CA needs to do the process.
You can try to get more PLUS loan, too.