This is the exact reason that when I was selling sewing machines I would try to get a feel for what the person intended to do with it. If they had never sewn before I would encourage them to not get the latest and greatest with things they wouldn't use. I've had people say but I have to buy the most expensive to get a good one. I've had people trade up within the first year but Viking has a good program for that with full price toward an upgrade. To me that's the smartest way to work your way up to a higher priced machine and seeing if you're really going to use it.
I wouldn't buy anything off Craigslist unless I could use it and see it and even then some problems are intermittent and you wouldn't know about it. Maybe if they had a clean bill of health from a service tech?