I have worked on regs since my college days; and there is no way in hell that I would allow anything to leave my bench in that condition. Was there any documentation of when it was previously serviced? If there is that much verdIgris on the surface, you can just bank on some internal corrosion.
I store a good amount of equipment that is used on a seasonal or irregular basis -- and there is absolutely zero corrosion on them, upon unpacking -- or that would entirely on me. The regulator below was stored, properly, well over a year.
You do have protection through eBay and Paypal; it's built into the transaction. If you had followed my recent thread on the same subject, refunds can be had, even if the seller offered no returns in his or her listings.
More often than not, the seller is well aware of the existing issues and won't even bother with the expense of having the equipment returned, as was the case with a friend who recently found himself in a similar position -- who, surprisingly enough, found himself buying items from overseas . . .