Nitrous mafia is really a thing. If you go to any type of festivals, there are going to be dudes who will go pick up some tanks (doctor office, grocery store surplus). Tank may run you about $300 tops, sell ballons for $10-20 bucks and you are getting paid. There is a difference between automotive, medical, and hospitality based tanks as well.
Im not someone to do nitrous , had a job in college where we would go hit up local festivals and sell bongs, pipes, etc. It is a surefire way to get paid, but getting caught or having someone stroke out makes me not want to get into selling ballons. Plus, its a nasty habit. Just smoke a blunt or eat some mushrooms/edibles. Better for you in the long term
These guys came straight up out of Philly, were the first to do it as a collective. Before it was one burn out in an VW van, now it is whole groups extorting other folks who try and sell ballons without being part of them.