Mice can get through an opening the size of a dime. Protect your goods; boxes, clothing furniture by using a dryer sheet and/or mothballs placed near the opening to discourage them from nesting in your unit.
Sofas and love seats can be stored on end to save floor space. Always place protective plastic UNDER them.
Caution: Do not store anything COMBUSTIBLE, i.e. paint, thinner, gasoline, solvents. Any item with a gas tank (auto, lawnmower, tools, etc.) should be stored with an empty tank.