Let’s be fair, you can’t change the locks on your son, he has nowhere to go, he has suffered from Anxiety and depression, maybe he is only capable of doing part time the the moment because of his illness.
Start charging him rent, if he finds he can’t manage on the money he has left, you will soon know if he is too ill to work , or that he just can’t be bothered.
He will need a fair amount of money to cover deposits and rent on a property unless he shares………
If he works full time, then charge him a fair rent and start making him live by your rules.