Grow plants for free by trimming off the tops and popping them in a container with a bit of water, keep topped up and you will have a continual supply of fresh greens to hand. When they get a bit bigger put them in a pot or straight into the garden and they will grow for you to harvest. Add a bit of compost, a touch of fertilizer and your kitchen top garden will keep on going. The plants above are beetroot, carrot, celery and chinese cabbage - try them all out and see how well they grow for you.
Ever thought about generating your own electricity ? Growing your own food, living sustainably ? Maybe keep a chicken or two and some animals ? Living off the grid may not be for everyone but for enthusiasts its the bees knees and you don't need to go totally off grid to become a part time urban farmer.