When will we be able to hire NPC as crew, will it be at first when they appear?

For 3.0 no, they're still working on some of the NPC elements of having them interact with you and have them be more than just a person filling the seat. They want them to have emotions, how do they cope with a crew member dying, are they getting paid enough. They also are working on the mechanics of them and having them do the jobs you want them to do. Their goal for V1.0 of that is to have a mostly complete experience where right now for that there's still some pieces missing.