What are the conditions for a designated beneficiary to manage their endowment if they are the rightful manager?

Primary text

When the management belongs to the beneficiary, either by the founder's explicit designation or because they are the most entitled in the absence of any other manager, and the beneficiary is a single, mature, and judicious individual, they have the right to manage. This applies whether the beneficiary is male or female, just or corrupt (Fasiq), because they are managing for their own interest, which is permissible in these circumstances, akin to a free person managing their own affairs.