how far do the strings have to be off the fretboard

[kagiso]

does the height of the strings off the fretboard affect the ability(of a beginner) from play barre chords?

[Garthman]

Yes. It is harder to play the guitar if the strings are too far from the fretboard. The guitar should be set up so that the strings are just high enough so that there is no "buzz" (caused by the vibrating string touching frets higher up the fretboard). If you are unsure you should have your guitar set up by a technician.

[KenW]

Assuming the fretboard and frets are level, the closer that you place your right hand to the bridge, and the higher tension string that you use, the lower you can set your action.