They never specifically said what the stipulations were for Yaz.
I would imagine that Yaz would get her money now,but then Tasha still would have been in charge of it so IDK if Ghost would leave a loophole like that for Tasha.
But he also can't leave Yaz out in the cold because of Tasha.
Ghost didn't know when he would die though,so he could have imagined that Yaz would be closer to 18 when he died.
But he allso had the foresight to think he might die before Riq graduated school.
I'm not trying to apply logic to this damn show no more.