If he still has parents legally, is it impossible to get their financial information? If they are low income, the assets section of the FAFSA can be skipped and it is just a matter of linking taxes electronically to the FAFSA. If this is not possible, you could try to get guardianship or he could try to get emancipated (very difficult) https://www.courts.ca.gov/selfhelp-emancipation.htm#:~:text=There%20are%203%20ways%20to%20get%20emancipated%3A%201,You%20are%20at%20least%2014%20years%20old.%20
Otherwise he will have to wait until age 24 to get financial aid based on his own income.
He may change his mind about a gap year. If COVID continues, there aren’t a lot of opportunities for that year. I would make sure he applies just in case.
I would not put financial aid on his shoulders at all. Most of us handle that for our kids and the financial aid offices actually talk to parents, unlike other college depts.