I bought an elliptical from someone on craigslist. It was either spend $6K on a brand new machine or risk $1.2K on a used machine. I took the risk, paid the $1.2K, plus $150 to have it delivered at home, used it 3 times and it died. The machine was in very good condition from what I could see but obviously there was something wrong with it. I contacted a repairman at a local gym and he said it was "the computer" and needed to order the part which is about $300
It's been about 2 years and I haven't gotten around to getting it fixed or even throwing it in the trash as it's just sitting there taking up valuable space.
So, my advice, go for the safest you can afford, I often think that I would've been better off spending the $6K, even if I didn't end up using it for whatever reason, I could probably sell it easier than this piece of crap.
Good luck!