I would make sure that the seller description means that the base is the wooden case that is cracked and can be repaired or replaced. That would be okay.
However, I have seen one recently posted on my local CL that the actual metal bed of the machine is cracked. I would not want to try and deal with that. Whatever cracked the metal probably also did some damage to other parts of the machine unless it was a flaw in the casting.
Good luck.