Only if there is an explicit guarantee of work. They are asking you to give up something, you should be compensated for that. I would get them to sign an intent

Only if there is an explicit guarantee of work. They are asking you to give up something, you should be compensated for that. I would get them to sign an intent before I would sign an NDA. This way they are bound to contract you if they move forward with the NDA. You still have a right to say no to the work, but they are protected from you saying no and then implementing their idea. I think it is a fair middle ground if they have a problem with the intent they are just wasting your time anyways.