Can people change?

i am talking to this guy who is incarcerated but he gets out this year in july i was wondering can it be possible for him to change and not go into his old habits a few of my friends say no cause he was maing to much money doing what he was doing and it will be to much temptation not to and a few say he could change but im not sure and 1 actually said i should be more worried about if he has a std