The sale of a homebuilt/experimental category amateur-built aircraft—either completed or under construction—adds a few variables beyond the change of ownership of a factory-built machine. The buyer may not have experience flying aircraft that don’t meet FAA requirements for such things as stability and control and may not have realistic expectations about his/her ability to fly it.
The seller may be the builder and/or the primary mechanic for the airplane and is rightfully concerned about being sued if the buyer rolls it up into a ball.