I think it’s a waste of your money. People who don’t know what it is won’t care, and people who do know what it is will just get it themselves.
I wouldn’t trust a carfax printout provided by a car owner anyway. If I trusted him not to lie, I wouldn’t need the report. If I don’t trust him not to lie, why do I trust that he didn’t just print out a fake report?
Someone who thought they might get away with it? Used car sales are notoriously (if maybe not fairly) considered to be rife with dishonesty.
My point is that the car buyer already has to trust that you’re honest in order to accept the report. If they already trust you, then you don’t need a report. If they don’t trust you, then they won’t trust the report. Or at least they shouldn’t.
I came across that once. Used Lexus, suspiciously cheap, dealer’s site linked to the Carfax report which was relatively clean. I was interested but first used Autocheck and it reported a major accident and frame damage to the car.