No but make sure when you see a machine the original system install discs come with it as disc one contains Apple Hardware Test which checks out logic board, memory, hard drive, modems, graphics etc.
Do not buy a liquid cooled model as these have had some major problems with leaks, and duck the original 1.6/1.8GHz single processor models. If the readies run to it look for what is known as a late 2005 Dual Core in 2GHz, 2.3GHz and 2.5GHz. These models run faster DDR2 memory and come with PCIE slots and faster PCIE graphic cards.