While it is permissible to pull water from a lake or river, the problems are potability and freezing of waterlines, so this is typically a seasonal source for uses other than drinking. Drilled wells (often called artesian here) are the best permanent source, with the probability of finding water in Maine being excellent. For an already developed property with a water source, water quality, quantity and the performance of the systems should be tested by a lab and/or a well contractor.