Is It Legal to Work at a Coffee Shop?

When i was 16, I worked at a coffee shop named stir crazy. There were regulars who would come around opening and sit at the shop for hours on end,. We had a self served coffee station, so they would pay for their initial cup and then help themselves to all the free refills drip coffee that they wanted to enjoy. One such regular was a man who never spoke a word to me. His behaviour felt odd, and it made me uneasy. My mam mentond that he is shy and he does not like attention or being recognized. Him not speaking to me then sense. But this is blowing my mind. Those eyes that gave me the creeps at work were the same eyes