It used to be a summer resort and the area around the lake is full of cute houses which were originally summer cottages and have been expanded. Houses around the lake can join the lake association and use the beaches. There's also been a lot development in the area in the 50's to the present, so it is pretty heavily built up. The stretch of route 6 that runs through Mohegan Lake is one of the worst, with lots of stores and the massive Cortland Town Center shopping complex. A good part of Mohegan Lake is in Cortland, actually. The town line seems to cut right through the area with a "Mohegan Lake" PO address. Both the Yorktown part and the Cortland part are in the Lakeland School District.
Here's a website:
http://www.moheganlake.org/