Need suggestions

I received a call from one of the project managers who requested my support for 2 to 3 months. He assured me of assistance with my band, promotion, and agreed to my requested location. However, the working hours are from 5 PM to 2 AM. I mentioned that I would need support from the team to work on the project, and he agreed to this as well.

I told him I needed time to consider because I am currently discussing another project that aligns more with my career aspirations. He said he couldn't wait because this requirement is critical and he needs to allocate me today to start working immediately. He promised to release me from the project after 3 months if I don't like it. However, I am concerned about what will happen if he resigns before then.

The role is similar to my previous one and not aligned with my aspirations. For the role I aspire to, no one is considering entry-level candidates, making it difficult to gain the necessary experience.

Could you please suggest what I should do?