Zero as we paid to put in a borehole. You needs the landlord's permission and viability depends on the area. I know they are not allowed in Arabian Ranches.
I grow lots of different types of tomatoes every year and get huge crops. As they always go in fresh soil in big pots, I never bother fertilising. I have in the past, but it never seemed to make any difference.
I water once a day as they are in lots of soil in terracotta. I find all plants dry out quicker in plastic posts.
It is worth pulling off the additional small side shoots as that is just a drain on the plants.
