For-profit businesses are not legally allowed to accept volunteer help as they are required by law to pay at least minimum wage.
There are exceptions under the Fair Labor Standards Act for seasonal activities like amusement or recreational establishments that operate for less than seven months in a year.
Some for-profit businesses engage in arrangements where people volunteer in exchange for goods or services, but strict compliance with wage and hour standards is required.
The legality of volunteering for a for-profit business is a subjective matter with some seeing it as beneficial bartering while others view it as exploitative.