1⟩ Are you able to meet project timeline?
If you have a tight timeline, you need to know right away whether the freelancer has a conflict. Most freelancers often manage multiple projects; this doesn't mean they aren't the right fit for your project, but it does mean that they need to be able to balance your project against the needs of their other clients.
☛ Things to listen for: Project management skills. Are they confident about their ability to meet your milestones? What's their approach to juggling multiple projects?
☛ Follow-up question: "Is this timeline realistic?" An experienced freelancer should know whether you've allocated enough time, missed key steps, or aren't leaving enough "buffer" for challenges that are likely to arise.