Well, lung cancer can form within the early adult years or never. That's the nature of cancer. It's more or less spontaneous.
As for the coughing and losing his voice, this is a result of anyone who long-term smokes. Basically, smoking will take an enormous toll on your respiratory system, killing the cilia that keep debris out of the lungs, destroying the alveoli where air exchange with the blood takes place, and some people will need to have their larynx removed, essentially causing them to lose their voices.