Example of Intracompany Organization

Summary:

We have one legal entity with multiple business units in this case if necessary to set up Intercompany Balancing Rules ?

We have this specific scenario

One BU sale car parts the other BU is a sale services workshop

the second BU buy car parts to the first BU and used to their reparation and sell the services

Under this scenario what is the best practice to manage this flow

Thanks