Is it permissible to go for Hajj at the father's expense when the young man does not possess the means for Hajj?

It is permissible for a Muslim to perform Hajj with what others have gifted him, according to the consensus of scholars. The correct view is that Hajj is not obligatory upon him unless the giver is his son, in which case Hajj becomes obligatory for him at that time. And whoever reaches Mecca with his own expenses or the expenses of others, and then performs the obligatory Hajj, it is sufficient for him.