The 2009 MBP had 3 models, 2.53GHz, with only the 9400M GPU and the 2.66 and 2.8Ghz models with both the 9400M and the 9600M GT, so check which one you would be buying for that 900 dollar machine.
If it is the 2.53GHz model that price seems a little high. (IMO)
Otherwise, I have been very happy with my 2.53GHz MBP, though it is getting a little old now, and compared with the new models it is about half as fast for intensive jobs. You may be better off buying a refurb 13" from Apple.
But according to the link I posted, the MB470LL/A is a 2008 model with 2.4 GHz processor and dual GPUs?