How long will it take to become a neurosurgeon?

It takes a long time to say the least. First off, most medical schools require applicants to already have a degree, so there's 4 years college, plus another 4 of medical school. The average age of students in my cohort was 24 when they *started* medical school. After you finish, you then need to get into a training program for the specialty you want; training is around 5 years give or take, depending on specialty. However, it often takes multiple attempts to get in, especially something like neurosurgery (which is one of the most competitive specialties there is). Also, depending on jurisdiction, you might not be allowed to start training straight out. Where I live, for instance, you have to be a junior doctor for 2 years before most specialists programs will consider you at all (in practice, it usually takes longer than that to have any real chance of getting in).