Which type of Business Unit should be assigned to employee?

Hi there, as a newcomer to JDE HCM world. I am not sure which type of Business Unit (i.e. BS or IS) should be assigned to "security Business Unit" and  "Home Business Unit" when adding a new employee in JDE HCM. The right choice in my mind is that the same "IS" type BU shoud be picked to populate those two fields . Am I right? Can anyone help clarify this? Thanks in advance.