Advice on a 12 footer
My all time favorite "Learn to sail" small boat is the S&S designed Blue Jay. Just a neat all around boat. I have seen prices range from 500 for a project, 1,000 for a usable boat, and over 2,000 for the ones used for junior club racing.
Jeff''s comment of having a "kicker" for the lulls is good, but will by default add a great deal of cost to the deal. You will need a b oat that could handle the weight and mounts needed. My last Lightning (the Blue Jay''s bigger sister) had a British Seagull for the light stuff on Long Island Sound, ie: the 5 O''Clock lull. Carvel planked white cedar hull... but I digress...
In the 12 - 14 foot range, paddles and oars for your auxiliary propulsion, then above 16'' a small O/B would work.
Hope you enjoy whatever you find.