Your logic is flawed, no one will buy an address, you have the private key, how will people know you won't store it to use their Bitcoins.
My logic is not flawed, if you dont trust an internet stranger to not run with your money then dont do this.
It is just an offer.
If you buy a cascasius coin , he has the private key , too.
I am willing to provide dox so you can come after me if this happens.