Some of the smaller sailboats (Sun Fish, Laser) are designed to tip over when pushed too far. I have a Laser and think this is fun in the middle of the summer. But it is not a boat to go out in a fleece and jeans in the spring and fall. This aspect should be strongly considered.
I have bought boats through the Want Advertiser. Here is the online link:
www.thewantad.com
A terrific 'dry' boat is the O'Day day sailer.
Good luck.