Answer:
The answer is nineteen years old.
Step-by-step explanation:
The text mentions more than once the character's stage in life. For example, "the Ohio village boy, was fast growing into manhood", or "The mood that had taken possession of him was a thing known to men and unknown to boys." It mentions he is moving to a new city to look for work, and that he felt grown up. So it is implied that he is old enough to get a job, but not yet a full grown man.