If you are not interested in racing try to find a design that you can build out of foam/glass. Build as light as possible, it's a real plesure to have a light boat when you have to carry it around.
Tortured ply hulls are fun to build, but the outcome is never quite sure, and it's involvig a lot of filler and sanding...
And last, don't dream of second hand value on a homebuilt boat.