I think that if you can verify with both your freelancer and the third party, all together...and everyone is aware of the situation, I don't see the problem.

Once you pay...how the freelancer wants to be paid, whatever happens after that is now between the third party and the person you hired. You are now relinquished of all responsibility and you don't need to pay anyone else anything...

It isn't your responsibility...and if what Garrett says is true...that you'll end up not paying him at all...then I don't see how that is ethical or moral to begin with...even to consider an option such as that.