USC is one of the most expensive schools in the country. You just don’t need to worry about any of this until/if he gets accepted then get FA information within a week or so after that. With SCA, 96% of applicants won’t have anything to work out because they were not admitted. Not to be negative, but I would spend time making sure other options are lined up. Until you see an acceptance and the FA package, there is nothing to with USC but worry needlessly. Wait till you have more data.
Assuming you applied for FA, you can google scholarships to apply to inside of USC (most had due dates of Feb 1st but there may be some, not sure didn’t apply to those) and outside of USC if your student has time to do essays and applications.