I'm going to have to completely apologize - I read your original post way too fast. I thought you were saying that the place you were going to buy it from *new* was essentially saying that "some of these units have a startup problem" as his review of this product...
...but now as I re-read it and I'm not feeling like a jerk I see that you are going to buy one USED from somebody who says that this particular one is having a "software startup problem"... I get it. My bad.
I agree with the above poster that suggests a restore back to factory settings. It's probably been hacked the wrong way. Unfortunately, if he has hacked it and now wants to get rid of it, he probably has already tried all of the simple stuff to fix it himself or he wouldn't be selling it.
Maybe find out exactly where it's failing? Does it happen every time or intermittently? Did he buy it from an authorized dealer? Can he give you a receipt?