Like Thisguy said, I would imagine that if you're at a Corps of Cadets school (Citadel, VMI, Norwich, Texas A&M, Va Tech, Maritime Academies, others?) you'd be living together, but neither of the schools in my batallion (Boston College, Boston U.), the schools at the other half of the consortium across the Charles (Harvard, MIT, Tufts), or any of the schools I visited when I was in high school (Tulane, Virginia, Vanderbilt, Georgetown, George Washington, U.Penn) mandated that mids live together--that being said, there's a good chance you'll end up choosing to live with ROTC friends for your sophomore thru senior years (freshman housing will be random) anyway.