Thank you everyone for the responses.
So far the owner had not been able to find a Bill of sale from when he purchased the kit. This is a Bede BD-5 aircraft. The current owner said he purchased the untouched kit from an American who bought it directly from Bede.
He has sent me a lot of pictures of the aircraft and of the pictures of the build process. I dont know how many pictures are sufficient, but I can tell you from the pictures I have that there are shots of almost every major stage of build being done. They are quite old pictures as this project was started in the late 70's.
The owner was indeed building it for himself, although he was a professional aircraft builder specializing in sheet metal work (he is 94 years old and worked on the F-104 starfighter!)
I can obviously acquire a bill of sale from him, and even a written statement that he was building it for his own personal recreation/education.
It sounds like from what I have heard here that absence of a BOS from Bede to the original kit purchaser and a BOS from him to the current owner is going to be a showstopper. Have I misunderstood? Are there any other options?
I really like this aircraft and he is selling it for a song... but ultimately I want something I can make legally airworthy.