Is there any rule about the number of times a check can be sent to a specific person?

There is not. That is really up to your group in terms of how you decide to operate. It is definitely a good conversation to have early on as the members of your group decide how your group is going to function and operate and what the group is specifically set up for. 

You might find it helpful as a group to come up with a written document in terms of a commitment or covenant sheet where you detail the vision of the group. This can evolve as you progress as a group and see what works well and what might not feel as good. It really helps new group members joining your group to have a good understanding of how things operate and what kind of needs your group meets and how it does so. 

Common Change has a strong focus on empowerment over handout and so we are constantly looking at trying to find healthy ways to meet needs that empower people and help get them on their feet over becoming a source of co-dependency and so this might be something you keep in mind as you draw up some form of steering document.