If the new hire can pass the department's written, oral, and physical ability testing and pass the medical screening, then we can train them to do the rest of the job.
Previous fire and/or EMS experience can be a plus, or it can be a negative if the new firefighter can't adapt to their new department.
My department recruits nationwide, and we lose more recruits to homesickness than to an inability or unwillingness to do the work.