Op- I have an idea but I’m trying to get a better feel for your son.
Is your family chassidish? Has your son learned in litvish or chassidish yeshivos in the past? Where is he coming from?
There are 2 schools in South Florida with dorms that may still be accepting applications. There is one in Miami Beach (the name eludes me) and another in North Miami Beach - Yeshiva Toras Chaim (DACHS).
I have also heard good things about the Skokie Yeshiva.