When I quit smoking, I did gain a little bit of weight. But within 6 months later i notice a lot of health changes.
1) Sinuses and eyes seem to be clearer. I didn't realize my sinus and eyes were a problem.. but a few weeks after quitting i noticed the air i breath smells freshers, my eyes stop watering.. etc. Meaning that while smoking i was obviously damaging my eyes and sinus.
2) Heavy breathing doesn't lead to needing to catch breath as much. When i was a smoker, after a 15 minutes of running, i would cough and have wheezing as i try to catch my breath. 6 months later NO COUGHING OR WHEEZING AFTER RUNNING
3) When I got completely past the cravings to smoke 1 month in, I also got a huge boost of energy!
And now that I'm following this weightloss path, i know that my 30 min runs would be 10x harder if i was coughing and wheezing, with no energy. So even though i gained a few pounds ( fat already so they werent even visible.) I'm very glad i quit.
I advocate quitting for anyone!
And trust me, after 2 weeks your cravings are just barely a whisper in your stream of thoughts easily ignoreable.

Also sugarless gum and celery helps!
Now its smells gross when I smell cigarette smoke. EWW
Anyways it will for sure HELP your friend lose weight! Maybe not in the first month, but after that they will have a big difference in their body. With the extra cash to maybe buy some healthier food!