<p>Summer in optional, in the sense that every quarter is optional. You are never really obligated to attend during a specific quarter.</p>
<p>As such, once students are ready for co-op (usually at the end of their second year) they will go on co-op during whatever quarter they choose. Summer is the most common, as there are more companies looking for interns, and there are less classes offerred.</p>
<p>If you are in RIT housing, you will usually need to move your possessions out, excepting special arrangements with roommates. (Though a storage cube for a quarter is vastly cheaper than housing)</p>
<p>Getting housing when you return is unknown to me, as I have only had summer co-ops, and housing after the summer is much easier to get.</p>