I'm looking to buy a Roland SP-404 SX and have found one used on Kijiji for $350. I don't know very much about samplers (besides some basic internet research) and have never gotten the chance to actually use one. What things should I be looking for/testing out to make sure I don't get sold a broken product.

left and right inputs and outputs are working, headphones jack working, pads not broken, etc.

they're like tanks - so unless it was severely abused, all knobs and pads should respond.

Thank You