I'd second the Hobie 16 nomination. Tough boat, lots of them everywhere, easy to repair and relatively cheap to maintain. I'd argue your best off finding one above $3K that has been nicely looked after.

The Prindle 16 is a fun boat and easier to sail than the H16, more reserve buoyancy forward, but all 3 on my beach have suffered from various major structural failures. These are older boats but 2 out of the 3 were in great condition before the hulls started cracking (repairable). The real fault is the rudder system basically sucks, as the locking pin works loose from the blades over time. Lots of used H16 rudder parts, not so much Prindle.

Another boat worth evaluating is the Hobie 18. Its fast, fun, tough (except for 1984-1986 boats) and easier to sail than any of the 16' boats. I suspect the Prindle 18-2 is a touch faster than the Hobie 18 but also easy to handle.