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.

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.