Originally Posted by Genden

I would not go to try out the machine alone and I wouldn't take cash with me. I see a red flag. If you are still interested, take someone with you to look at the machine and try it out. You can evaluate the situation with the safety of someone with you. Often sellers request cash because they don't trust a check and that is understandable.
i may be unnecessarily suspicious, but if they don't actually have a machine but are only interested in taking your cash when you get there, that may be the reason they don't give you a serial number. It pays to be cautious when answering Craig's List ads.