If you invest in a how-to book like "Building Skin on Frame Boats" by Morse you will get everything you need. Traditional SOFs can be made using anthrapomophic
dimensions. Body related incrementslike size of fist, span from fingertips to elbow, span of outstretched arms. A kayak under that system would be much smaller for a person the size of uour wife.
In regard costs, there are builders who claim they can knock out a boat for $100. If you can scarf joint you can make your long stringers out of short sections of scrap lumber.

: I recently finished a expedition single strip built kayak and am interested
: in trying a skin on frame.What is the average cost to build,hours to
: build,pros and cons,plans? I really know very little about them except
: they look light. My wife says I should build her one.