You don't "rent" a flight club airplane. Renting would imply that the aircraft is operated for hire, which would then require that the airplane be commercially insured and undergo 100 hr inspections (something that the members of the club might not be willing to do) many clubs will allow a CFI to teach it's own members at a fixed rate (sometimes they will allow the CFI to set individual rates). The problem with going the flight club route as a source of income, is that your prospective students might not want to fork out the money required to join the club.