Have you checked any online courses? Some of those are less costly.
Where I am, dual enrolled students receive free tuition for college courses taken at the local CC or local state U branch. The HS pays for those. Have you checked with your HS guidance office?
For your son’s actual college enrollment…his job now is to get the best possible GPA and the best possible SAO or ACT score so that he will have good college admissions prospects…either to schools that meet full need. Or to schools where he could garner significant merit aid.