The federal minimum wage is unconstitutional. It applies without regard to whether the work in question involves "commerce ... among the states."
In any event, minimum wages in general, I hate to say, are coercive and opposed to the liberty of contract. If someone wants to work for two dollars an hour, I don't think that the government is entitled to stop him from doing so.
I would agree that the federal minimum wage is probably unconstitutional as an enforcement of the interstaet commerce clause.
However, I do not think that anybody in a position where they accept a job for $2/hour actually wants to be paid that little, it is quite probably because they have to accept the job or do nothing and starve.