The Rambam writes in Mishne Torah Hilchot Melachim uMilchamot Chapter 1:
Neither a butcher, barber, bath-attendant, nor a tanner should be appointed king or High-Priest. This is not because of an inherent fault, but because their professions are less prestigious, and the people will always treat them lightly. A person who has served in one of these professions for even one day, is disqualified for the monarchy.
How much work do you need to do to be considered one who has worked in the profession? Eg: How much meat cutting makes me a butcher? Shechting? Cutting off a limb? Trimming the fat off the brisket? Weighing the deli meat and putting a sticker on the bag?