Its age related, or possibly glow plugs like Jimmy described. I wouldn't be worried at all with a half a second start time. Ol' Turbo is instant, but Norm takes a crank or two to get going (less than a second).
I never had to give Ol' Turbo any gas at all to get it smoothed out during cold starts over the winter (as long as I remembered the glow cycle).
I would be concerned with 560's 190D if he didn't sell it already.