None. A man must live to the age of majority.
Dylan was addressing Americans, so the answer is: Walking roads has nothing to do with it, so it’s kinda offensive to people who cannot walk. A male child becomes a man the moment he is aged 18 years.
The answer is not blowin’ in the wind.
It just occurred that the author of Ecclesiastes (both) listed various human endeavors, pronouncing each Vanity and chasing after wind (which is inane in itself). Dylan says the answers to his questions are blowin’ in the wind. His questions seem to be hypothetical or otherwise unanswerable. Therefore Dylan says it is ridiculous to seek the answers to these questions.
…Perhaps not when the answer, my friend, is 18.
BONUS: The meaning of life is 42.