Student Living Conditions and Frats

My son has UM on the top of his list, but if you gets in I am worried that the statistics show most students live off campus. Is that because there are not enough dorms or other reasons? Is it hard to find off campus housing? Also my son says he is not a Frat type of guy and I have mixed messages about what percentage of the guys are in Frats and what he would miss without joining one. section F1 says that 16% of male undergraduates at University of Miami join fraternities.