I have always found it impossible to be a "bill collector" and a teacher at the same time. For example, most physicians will not have anything to do with the money side of their practice. They have someone else who does that.
Here's a quote from our dojo policy:
"It must be understood that our dojo is not a commercial enterprise in the common sense. Sensei are not merchants and we do not offer goods, commodities, or sevices for sale. Budo is a priceless art. The teacher/student relationship must be preserved in order to learn properly and transmit this art from master to apprentice. Money is not and will never be the primary consideration in our relationship. However, practical matters demand that bills be paid, etc. We must carry out our financial responsibilities in as business-like a way as possible. Please, always feel free to discuss financial matters with the dojo kancho."
I prefer to not even get into the money aspect of students' practice. One of my senior students handles it for me. No one is ever turned away for money problems unless they show that they are unwilling to be responsible for their commitments and are trying to get a free ride.