If it's parked on stand for a length of time, check underneath it for oil spots. It can only leak in one of two places, at the input or output shaft on the gearbox. As mentioned, if it leaks, check the gearbox to see how much fluid is in it. Also, it would be ideal if the seller could hook it up to a tractor and spin it a few rpms so you can see if the auger (or the output shaft) might be bent, or if the PTO shaft might be bent. Lastly, since you have a Yanmar 2500, you might want to verify that the PHD will fit it well, and that it will lift it up high enough to keep from dragging the tip. Some smaller tractors have a little trouble with that part due to the geometry of the 3pt parts.