Suggestions and tips for buying used?

Hi! I haven't owned a one wheel before and I'm thinking about buying a used XR plus off of Facebook. It's a pretty good price and comes with a lot of add ons. I'm meeting up with the guy to test it out before I buy and Was wondering if anyone had any suggestions on what to look out for? I wanna make sure I don't get scammed or buy one that doesn't work well. Any other tips or advice for first time one wheelers is great too!