You can only link to the profit center if you have created one in Controlling (CO).
In Customizing for Real Estate you can:
Choose the profit center account assignment of Real Estate
Or use the account assignment of the controlling area.
Profit center inheritance
A profit center is inherited to subordinate objects:
If, in the object hierarchy, you have not specified a profit center at the lowest level (for example, lease-out), the profit center of the higher-level object (for example, rental unit) is used when you make a posting.
For detailed information on profit centers, see Profit Center Accounting (RE) .