Obtaining title on ATV

I am currently looking at purchasing an ATV second hand. Story is they current owner purchased the ATV from the original owner. He has title and BOS on hand, but he did not get the title put in his name. I call the local title place and they told me he had to get the title transferred to him or I would be double taxed.

He is now going to do such. How would I know he does this though so I am not double taxed? Will they issue a new title in his name? Also they said I have to have proof of insurance. Why is this required since it will not be on the road to register?