Growing a garden in your back yard will save you money on your shopping bill now, but will literally save your life when aliens invade and the world destroys itself fighting off the invasion. People are doing miraculous things with very small space, turning typical suburban back yards into teeming microfarms that produce a wide and tasty array of fruits and vegetables. It might not be a bad idea to invest in a few robot machine-gun nests to protect the crop after the invasion.