Debería considerar trabajar con UNION en lugar de JOIN.
Si simplificando su consulta, la unión podría verse así
SELECT dbo.Stu_info.Id_num, dbo.Development_fee.Dvf
FROM dbo.Stu_info
LEFT OUTER JOIN dbo.Tuition_fee ON dbo.Stu_info.Id_num = dbo.Tuition_fee.Id_num
UNION
SELECT dbo.Stu_info.Id_num, dbo.Registration_fee.Reg_fee
FROM dbo.Stu_info
LEFT OUTER JOIN dbo.Registration_fee ON dbo.Stu_info.Id_num = dbo.Registration_fee.Id_num
