Mine is pretty basic, there is a borehole situated in the corner of the field, about 300m away from the house and maybe 20 metres higher up. It is about 2 metres deep and a metre accross the top, concrete sections. The water runs downhill to the house in a single alcathene pipe to a 'water house' which was bypassed by the last person who lived here, and then runs straight to the taps.
To put a new one in there are bound to be loads of requirements, filters or UV treatment, but if its an existing system I wouldn't bother with the filters or UV myself. You can have the water tested to check its safe or to check its mineral content/parasites etc.
I'd def see it as an advantage in a property, you'll be saving 400 a year which adds up over time!