Personally I would never use second hand food processors without first stripping and examining them internally unless I knew the full history of previous use.
[1] there may be bio-hazard contaminates inside the casing from previous use.
[2] the mechanism / electrical parts may need repair / replacement. Being competant to do these types of repairs means I would attempt them as it doesn't cost me anything other than time. If replacement parts are needed then I weigh up cost against benefit.
