I think that if you grow for personal needs is easy to stay from police sight. There is no need for finding dealers and you can live normal life far from street and if you are not seen on streets and don't have contact with drugs world chances that police is gonna bust you are very small (except if neighbor don't like you and figures out that you are growing).
If you grow with intention to sell then it is normal that you will have business with police. I am sorry to hear what happened to your friend but if he was busted then he serves his time knowing that money awaits when he is out. Everyone who does illegal business should be prepared that in one moment will be locked up and always have stashed money in amount that is ok to do time. Bribing police for avoid one year sentence is for me throwing money away. I was in jail for 14 months and it passed in a blink. Time spent serving obligatory military service was mush harder for me. Money stashed in time before getting cough I would never earned legally in those 14 months. Once again I feel sorry for your friend but also have opinion that he played it wrongly.

Conclusion is that if you grow for your self and never sell neither a joint you are not doing criminal business