My dad and brother and I rented a small sailboat in SC when I was in college. Almost sank the thing by running into a marker. My Dad had sailed a decent amount 40 years earlier but hadn't done much since. The only other experience my brother had was when he was really young. He and my Dad rented a cat somewhere in florida and had to be rescued by the coast guard after it sunk because my brother took the plugs out before going out!
Then my Dad bought a catalina 25 and my brother and I drove 4 hours each way every weekend one summer and learned how to sail the thing. Trial and error and reading books. Don't know why I ended up liking it so much. We then bought a Pearson 303 and sailed that for years and I soloed it across lake michigan a few times.
So, in answer to your question... I guess one has to have the interest to start then the availability of boat to learn on.