My home club (Hopkinton) does not allow paid instruction except for the classes offered by the club. There are valid reasons for this policy:
1. The club liability insurance covers officers, directors and "persons acting on behalf of the club". It's hard to argue you are acting on behalf of the club if you are just renting the facility, but easy if the club is getting paid directly by the students.
2. The club is a volunteer org. The club's instructors do it for the good of the shooting community and the club, and are not paid. It makes little sense to let someone else come in an enjoy the benefits of the upkeep of the club in return for a portion of the class fee when club members are doing the same thing but letting the club keep all the excess of revenue over cost.