Cao Zhen, under normal circumstances, doesn't want to take on any disciples. Taking on a disciple means providing them with a lot of resources. How poor is he now? He already has eight disciples; taking on another one would really drain him dry.
But Ruo Yun the Immortal is different; this woman is a reincarnated great ability.
A reincarnated great ability, when reincarnating, must have hidden away resources well, so she wouldn't need his resources at all. Perhaps after taking her as a disciple, she might even support him.
The only issue is to see what kind of person this woman is.
If she's an ungrateful white-eyed wolf, there's no way he could take her in.
Although he could observe Ruo Yun the Immortal at different times through China Cloud, to see what kind of person she really is.
But if he doesn't approach Ruo Yun the Immortal, how can they get to know each other first? How can he trick her into becoming his disciple?
Anyway, he doesn't intend to leave.