If its a good one and they have had it a while and it hasn't just been repaired so any issues will have been sorted then I can't see the harm, its just a case or remembering it wont be worth market value so if you get it cheaper, you'll have to accept you'll have to sell it cheaper. Also check insurance, some places wont touch them.

If they are fixed right they can like you say, be a great way to get yourself into a nice motor that otherwise would have been out of you league.