There is a book-length set of regulations at the federal level. All workers are required to receive health and safety training in specific areas. The feds mandate adherence to all building, fire, and health codes. All workers have to get comprehensive background checks, including fingerprinting.
There are strict and complex rules about the ratio of workers per child, in effect preventing economies of scale from driving down the price. Child labor laws limit the labor pool. And everyone has to agree to constant and random monitoring by bureaucrats from many agencies. Finally, there are all the rules concerning immigration, tax withholding, minimum wages, maximum working hours, health benefits, and vacation times.