I am having difficulty getting my head around a design problem. I have students in an apartment. The students incur fees and rent. Normally the rent is paid in full for the semester. But some pay in 4 installments. The student makes multiple payments. It seems to me that fees and rent and payments is a many to many relationship that requires a join table. Or maybe I don't need to directly need to relate them since they are both related through the student. Any opinions out there?