Buying a used flash?

This might have been asked before but I could not find using the search. Is there any issue buying a used flash (like bulb's lifetime). Would you buy a used flash?

Thanks

Without a warranty, I would pay no more than half the price of a new unit. But that's just my own risk-benefit analysis.

And I would want to be able to verify that all functions of the unit, mechanical and electronic, were in good working order.