I live on a lake and when I built it was the septic that was the concern.
My well was drilled. Drilling here (CT) is running at aabout $6 a foot. Add in a bit more for steel casing (needed until you hit bedrock), as well as pump/elec/plumbing...most wells run abouut 200' deep and cost $3500-$4000.
Septic is a can of worms. A conventional leach field here is $2500-$3500, more elaborate ones can run $7500-$10000. If you get into an engineered system, the sky is the limit. They can run as high as $30000-$40000.