It is unlawfull to allow anyone to work for free in a for profit organization in the USA. Volunteering is for non profit organization. And since workers comp and unemplyment insurance premiums are based on an employees pay you would not be covered by their insurance, which any good business person would refuse to allow!
TRy to get an entry level position at a low wage. Minimum wage is like not getting paid. Maybe some will give you a try for that!