I'm an instructor and can tell you from personal experience that it really is tough to find a club willing to allow you to use their facilities to teach. Some have "their trainer" who teaches for the club so that not only are those trainers forbidden to make money but it actually cost them money to do the training.
When I became an instructor I visited a number of clubs and was told that they don't allow instructors to teach at their facilities. I teach my Mass Gun Law Seminar (strictly a sit down session in a classroom/meeting room, no range use at all) much more frequently than my NRA classes and they still wouldn't approve my using their space even if I paid to "rent" that space.
You do get more consideration if you have already belonged to said club for years before you become an instructor but that is no guarantee either.
Most of us are in Mass, so we don't know the clubs in RI and only the few from RI that are on NES might help in that regard.
Once you find a location, NES rules require that you pay for an instructor membership ($99/year) in order to advertise here. You would also be very foolish not to obtain instructors liability insurance (most clubs will insist upon this) for $1million which costs $320/year. And the few clubs that allow instructors are likely to charge you a fee to use their facilities. After you pay all expenses, you really aren't going to "make money", I can tell you that from personal experience too.