I have expressed my interest in the work of a professor. She does not perfectly match my interests but there is a good amount of overlap. Turns out that she has a PhD position open, with undefined topic, and that she would take me.
Can I, without commitment, suggest to try to find a topic of interest for both, and if the negotiation is not successful, opt out of the collaboration?
I find it quite dangerous to blindly accept working with her: maybe, later on, it turns out that what she specifically wants to work on now is not something I want to dedicate years of life to. On the other hand I appreciate that she will not want to take the trouble in working out a topic together, if I have not accepted being her student yet.