When I was living in an apartment, my bare minimum for each person was one case of bottled water (28 count), one milk crate with four gallons of water, and bucket of freeze dried food I picked up at Wal-Mart (I can't remember the serving count but it will easily cover 3 days).
Everyone also has a backpack with a bladder, emergency poncho, Mylar blanket, head lamp with extra batteries, pocket knife, and a basic first aid kit. The packs will hold 2 liters of water and all the food from the bucket if needed. The backpacks mainly used for when we go hiking but can also be used if we HAD to leave our home.