What is the ruling on the job and the money earned from it for a young man who studied from books bought with his father’s money, which is mixed with halāl and harām, and what must he do?

The statements of the scholars' madhhabs (schools of thought) regarding dealing with someone whose wealth is mixed (halal and haram) indicate that the preponderant opinion is the permissibility of dealing with him, though with dislike, unless the transaction involves the very essence of the unlawful wealth. Therefore, there is no harm for the young man in benefiting from his father's wealth, nor in the job he obtained with his father's help.