I don't spend anything on yard maintenance. Though I do occasionally buy new plants and use water. Things grow fine. I put weeds occasionally. And use an electric mower for the lawn.
Not only that I eat from my yard. In reality this doesn't save a huge amount, though it does save some. It is much more about getting yummy food that is also healthy. The amount I spend for tomatoes plants say is easily paid back with the food produced. My favorite is wine berries and those I paid nothing for (a bird helped me plant them, I think). I bought 2 blackberry plants years ago and they keep spreading and giving me yummy food for free.
I also feed the backyard wildlife (which include butterflies, chipmunks, hummingbirds, robins, crows, turtles, rabbits, hawks, love birds, bees, squires, woodpeckers, preying mantises, ants even a fox) by planting (butterfly bush) and encouraging plants (holly trees and bushes - transplanting little ones that sprout, berries that sprout, mimosa trees...) that have food for animals.
I also have plenty of flowers that just return year after year: First Flowers of Spring, Spring Tulips.
Related: Growing Lettuce in My Backyard - Eat food. Not too much. Mostly plants.