All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, praise be to Allaah Who guided and enabled him to repent, and we ask Him not to misguide him after He had guided him.
As to the money that he had earned from his forbidden business while being ignorant about its prohibition, and now that he has repented from that, it is permissible for you to benefit from what remains of the money he has at hand. Shaykh-ul-Islam Ibn Taymiyyah said, “Whoever repents, what he has in his hand and which he had earned from forbidden money is lawful for him, but it is better for him to get rid of the money which he thinks to be purely ill-gotten, so he should give it to the poor and needy, and the remaining money will be lawful for him."
In addition to this, he is not obliged to get rid of what he had bought with ill-gotten money, like houses, cars and the like because it is only the forbidden money that is forbidden, so if he gives away the forbidden money which he consumed, then what remains in his hand is lawful for him and he is permitted to benefit from his car, clothes etc. He is not obliged to get rid of them.
Even if he does not get rid of the ill-gotten money that he has at hand, then we have already explained that Ibn Taymiyyah is of the view that repentance is like embracing Islam which wipes out all previous sins. Indeed, Ibn Taymiyyah said, “Ordering him to give back all the money that he had earned and abandoning (getting out) of all the belongings that he likes, then repentance for him will be a punishment…”
Allaah Knows best.