What would he do on his own? What would have you done on your own as a kid? If these answers are different, why?

How will negative consequences be handled, like he doesn’t pay rent, runs out of money for food, or he damages the apartment? What about really big ones, like he allows someone to stay over long enough that they become an established tenant, cause problems, and then don’t leave? In your jurisdiction, are there legal consequences for you if he breaks the law that you would not face if he were legally an adult?

Is there a plan for if he decides he wants to move back?

Do you foresee any legal consequences? For instance, if his school learns about this arrangement, will CPS or the police get involved? Is that something you can recover from?

In the right circumstances, I think this is a good idea. As a parent, your job is to prepare him for adulthood. Letting him live on his own, while meeting his needs (food, shelter, healthcare) with a safety net can work. A lot can make these the wrong circumstances. Only you can answer whether or not the circumstances are right in your situation.