I do find often that buyers are concerned with shared well & septic. I never quite understood why other than the fact that you may have to converse with your neighbor from time to time about it if problems arise. Factors to consider are often who is billed for the electric if it is not separate meters for the well and if the shared well/septic is recorded. These are both certainly items that you can address in an offer if they are not. In my opinion there really is more of an upside to the shared well/septic. That is if either need repair or breakdown you share the cost with your neighbor instead of consuming it on your own.