Hello Snusie! The fact that you are voicing your fear about him influencing you is already a sign to yourself that you know you might have a weakness. If you want to try to develop a friendship first, be careful! Bad company corrupts good morals. If you go in thinking that YOU will change him, then you'll definitely be a failure. Ask yourself why you want to date him. Sometimes to goody two shoes the rebellious side seems exciting. Speaking from experience, I have a friend who was very similar to you and she liked a guy similar to the one you like. Long story short, she dated him, ended up doing drugs and some other things she wasn't proud of, and broke up with him. He dove deeper into drug use and she had baggage that she had to carry around with her from the bad decisions she had made with him. While she was dating him, she wouldn't really listen to reason because she kept justifying him. She also found him hard to shake so when she finally did, it was a relief to her.
So, if he is a real user, then be careful. Everyone has their problems, but drugs are one problem that can ruin your life now and in the future. I have an uncle who took drugs when he was younger then stopped and he is still paying for the after affects both physically and psychologically. Think to yourself, "If I were to marry this guy, what kind of influence would he have on our children." I know you aren't thinking of marrying him, but this is a good way to evaluate guys. I hope this helps!