Enter a rental unit or a group

What causes this issue?

In real estate planning for rental units, you can enter either one
rental unit or a group of rental units on the planning initial screen.
You cannot enter both.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Delete either the rental unit or the group, or
Enter a value in one of the two fields.

Error message extract from SAP system. Copyright SAP SE.