How to ck bottom end of used OB?

For example: assuming nothing is cracked and I can get the prop off(I wouldn't want it if I couldn't) and there's no noise(grinding) when I turn the shaft, how much movement, if any, to expect in the shaft? How much leakage, if any, to expect around the seal? Checking water pump output if it's water cooled. What else can a person look for to determine the condition without taking it apart? Looking at the oil is a no-brainer, but that could be changed very easily.

Thanks

How much leakage from a seal? None
Cant check the water pump without removing the gearcase. Pump assembly should be checked anyway once the engine is purchased.

If you are really concerned then have the engine checked over at a shop that has a pressure checker for the lower unit. Wont cost much just to do that.