how much ground space for climbing plant?

That depends on the variety of plant, the orientation (e.g., north side of the fence), and exposure (e.g., part shade). Some climbers require a significant root zone; others do not. On the south side of a fence in full sun, you might have to leave more space between the base of the plant and the fence so that air can circulate in the heat of the day and thus prevent the plant from cooking. On the other hand, a subtropical vine on the south side in full sun might need to be very close to the fence to receive re-radiated heat in the winter to prevent frost damage.

Yes I would say that make sure it gets plenty of water and that it is facing sun so that it can grow.

Why would you say that?

David

As a rule of thumb, I presume that the root system will need as much space as the foliage.