IMHO, the CSUs would be a poor choice for an OOS student.   The CSUs are mostly instate, and often commuter.  They also can be suitcase schools.   The weekends don’t have enough to keep kids on campus unless they join a Greek house.
Have we heard what this student’s major and career goals are?
If the mom is looking for low cost options, so that she can afford to either bring her son home for holidays or travel to see him, then she and her son need to be open to a variety of options.
Unless the son chooses a school that is a 2-3 hour DRIVE away from home, frequent visits will not likely happen.   It’s just the way it is.
My kids were 2.5 hours away from home.  My younger son, rarely came home.  My older son liked coming home about once every 3-6 weeks, depending on what was going on.  He has a very close friend who also liked coming home, so they’d carpool home every so often.  BUT…the issue is time.  Once you’re beyond that 2-3 hr drive home, coming home for weekends can be a waste…too much car time.   When my southern California niece went to Cal Poly SLO, it was “only” about 5 hours away from her home, but that was too much for frequent home visits.
That said, there are 3 day weekends, fall break, Thanksgiving, Winter Break and Spring Break which all afford longer times when a child (or parent) can travel for a visit.   Keeping college costs down can afford those trips.
The mom is concerned that if her son is too far away, she’ll only see him during the summer.  That would not be true if he comes home for Winter break, and other breaks.
The son is opposed to the south.  Why?  Which southern campuses has the son ever visited?   If he hasn’t visited any, then this is a good time for him to learn that preconceived notions are often…wrong.
Many southern schools are very cosmopolitan, drawing professors and students from all over the country and the globe.  Some have many very high stats students, yet stilll give excellent merit scholarships or need-based aid.