If you live in a house, you will probably need a gardener, especially if you are not used to keeping plants alive in the heat of the Madrid summer.
Most of the time, you will “inherit” a gardener from the previous tenant or from the owner of the house. You can also ask neighbours with beautiful gardens.
Don’t expect gardeners to work according to British standards. Overall, they know their job and will cut the grass, do the watering, keep your garden neat and tidy and plant what you ask them to.
Most gardeners are responsible for pool maintenance which is a good deal as a swimming pool is often more work than it seems.