I would't buy any processor used. First of all you don't know if it even works and secondly you don't know how much it's been abused. What if the person you buy it from tried to overclock it way past it's limit? What if they overlocked it with out good cooling? All these things could be a abuse that causes the CPU to either not work or shortedn it's life span.
yes that is a great, and in terms of getting through the next 3-4 years in depends, do you game? or is it just business work. im guessing you are a gamer because you wouldn't be getting a processor like that. it will do its part as a processor but only if you have a good enough graphics card. if you tell me which graphics card you have i can tell you if your good. if i wrote all that and your not a gamer and this is just for school or work, i would advise you to get the cheapest processor you can find that is around 2.0 ghz