Fruit trees are ornamental, and with a minimum of care, produce a LOT of food. Berries and grapes are very satisfying as well, you can get a lot of juice to freeze and use throughout the winter. I used to make jellies, but now stick to juices, because they’re better for you.
I use Pomona’s pectin for jams. It allows for big batches and low sugar jams.
I use 12 cups of fruit, 3 cups of sugar and the pectin. It makes 7 pints of jam; just one cannerload.
Although it seems expensive, I figured out the cost per pint and it’s way cheaper than Sure-Jell and Certo.
When I think back to my days in the city, it seems that city dwellers did better growing things in containers and empty lots than the suburbanites do, probably because of the very hot sunlight and fewer trees. I've seen city people grow large grape arbors, every kind of vegetable and lots of types of flowers. The surrounding bricks and other masonry seem to absorb water and then give off minerals and mist that are pleasing to plants.
Here in the burbs, we have many restrictions on how you can fence, where you can garden (must be in the back, not the front) and so many natural pests like deer, snakes, rabbits, voles, and massive hordes of insects, that it is difficult to garden at all unless you are in older, unrestricted parts of town with lots of sunlight.