I'd say just do some cold storage transferring. Put the money on a paper wallet with the private code on it, verify that the money is on it by letting them scan it, and when they get home they just transfer it to their own personal wallet.
Not a good idea. A paper wallet that you didn't create yourself means the private key could be somewhere else as well. The only way I would suggest using this idea is if the funds were swept to a new address that the buyer controls at the time of exchange.