What happens if I stop laser hair removal treatment after 6 sessions?

The amount of hair that remains after your treatments should remain constant. Sometimes hormonal issues may trigger the growth of new hair, but this isn't very common. Your six sessions were not a waste of money as they will provide permanent hair reduction. You can wax if you choose, but if you get to a point financially where you would like to resume laser hair removal treatments, I would stop waxing so you can get the best results from your treatments. 

There will be some regrowth of hair but not complete reversion. Waxing is fine after LHR and there will be no side effects related to your prior LHR. Typically, I recommend 1-2 treatments per year to maintain the hair removal after the initial sessions.

Whatever stage your hair loss is at is most likely where it will stay until you get more treatments.  In some cases hormonal changes can trigger new hair growth, but that is most common after pregnancy or a large hormone shake up.  
You can wax in areas that have been treated if you are not going to continue with laser hair removal.  However, you must stop waxing before you resume hair removal treatments.