"And if he designated her for his son, he shall deal with her as is the practice with free maidens." If a man did not have the privilege of studying Torah and did not study since his youth, whether because of time constraints or because he had no father to teach him, then he can make amends. He should teach his son.
For this son, indeed, needs that his be very compassionate toward him, not that he have to toil [for a living], and therefore have to abandon his study, but rather "as is the practice with free maidens" – who are not in the position to provide for themselves but whose father who provides their livelihood until they are married – he should fill all the needs of his son at all times.