You must not remember the days when folks put ads in the paper with their home number and address and folks came over with cash and bought whatever you were selling - I do, it was NO BIG DEAL. I have sold guns at garage sales (and bought some too) where we didn't even exchange first names, let alone our entire history.
So... clearly you exercise good
judgement and therefore should not need to perform any additional
due diligence. You do realize that your words represent a very strong case for universal background check requirements?
Taking this a step further.... as judgement is clearly not universal and there are already laws on the books, what methods are available to ensure that individuals don't sell to the prohibited?