Yeah, two different questions here:
1. Is the frame safe? Just based on one picture, odds are, yes, IMO
2. Should I buy it? Why take the chance when there are so many options.
If you could have someone with knowledge inspect it, and there was a fair discount over market rate, it would be worth looking into. If there was another frame of equal value that you were interested in, why bother?
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.