If he is not an A student very strong in math and science (especially physics), then you may want to set the price limit with a 9 or 10 semester assumption (and be aware of FA and scholarships often running out after 8 semesters).
Summer classes at local colleges are only likely to be useful for lower level courses or loosely specified general education. Upper level courses are less likely to be offered in the summer,band transferability may be less likely due to curricular differences.
Of course, a summer session is really an additional half semester of courses (though can be cheaper than half of a regular semester), and can prevent having a useful summer job or internship (commonly paid for engineering).