If it actually trains him and gets him ready for a job and is not preventing him from supporting himself currently, I see no problem with this.
The argument against unpaid internships is usually that it means only the upper classes get access to a jobs pipeline for the better jobs because very poor people can't afford to work for free.
But I've done freelance work at below minimum wage rates because I controlled my hours and was paid by the "piece," not by the hour, and that helped me develop skills and an income. I was homeless at the time and too sick to work a minimum wage job.
We let privileged people work for "nothing" in order to have a shot at something better. That's the typical deal for a lot of company founders.
Saying that non rich people aren't allowed to work for little or nothing in order to better themselves is a form of denying them rights and access to a better life. It helps keep them stuck in minimum wage jobs with no hope of a better future.
As long as this isn't some undue hardship, some bait and switch deal where he is enticed with promises you have no plans to fulfill and he actually gets value out of it, I see no problem with this.
Gambling on something better is a long human tradition. All people should be allowed to make that choice if they so desire.
They just shouldn't be conned into "gambling" on something with no real payoff for themselves like so many college students have done in recent years where they are saddled with student loans, the glut of degreed individuals means their degree isn't practically a guarantee of a good salary and the only people benefiting are the banks issuing the loans and raking in the interest.