Beware Ebay private sellers. I've found the store-fronts to be reliable. But when it comes to private sellers, I find an alarming number of them sell their "old gear" not because they no longer use it or want to replace it with something newer, but rather because the unit is malfunctioning and the seller wants to unload his lemon on some victim halfway across the country (who isn't likely to show up at the seller's door with a baseball bat, nor willing to go to the trouble/expense of shipping it back and filing an ebay dispute). The extent, or often the very existance, of the defect is never revealed by the seller, who hopes you either don't discover it before he gets his money, and/or he intends to deny the defect. I've personally heard the following excuses:
"It always worked for me. Maybe you're not setting it up correctly." -- For why a Studiologic VMK88's aftertouch didn't work. It definitely didn't work at all. "I never used that feature, but it should work." -- For why a Yamaha KX76's sustain pedal input didn't work. Guy claimed to be the original owner, and yet the pedal he shipped was not the Yamaha original. If he never used the sustain input, then why did he buy a third party sustain pedal for it?
The Roland RS-9 I bought has a habit of randomly spitting out maximum mod wheel values when you haven't even touched the lever.
And if you ever see an ebay ad where the seller writes that he "can't test the unit", typically because of a missing power adaptor or some cable he claims you can easily purchase, then that means "this item is broke, and you're buying it as is".
I endure this same struggle on an almost daily basis - Do I let Mr. Responsibility win? Or do I let my Inner Child have his toys so he will be happy? Usually, the Inner Child wins out. It's why I stay broke.