Non custodial CSS waiver with mental illness

Thank you, I have called one school and they suggested the waiver. But, then I read how difficult it is to get approved. I even considered doing the entire CSS application for him and the mom would get him to click submit. I don’t think that would be right but he has no money, trusts, investments. He has nothing and lives with his mother. She works for a big retail chain
and collects SSI. She has a limited income and no investments either. Would we need proof from the IRS that he is a non filer? He just wouldn’t be able to jump through all those hoops. Or would they accept moms taxes?