Workers are the backbone of any shop in Swords and Potions, without them there would be very little or no way to start a thriving business. Without the wares and goods provided a shopkeeper can't do the job that was intended.
Highest hireable worker to shop level percentage seen is 91% of shop's level. Average is however between 30 - 65%, unless shop is below level 10.
The maximum a crafter can be hired at is worker level of 100.
If workers are too expensive or you do not need them, you can fire them from the menu in the worker screen. If you go bankrupt, you also lose all of your workers (this includes all token bought level upgrades).