As a freelance, it's hard to make any real money from the 'hard news' sector of journalism. Feature writing (which appears to be where your interests lie) offers more opportunities. If you're really committed (to the tune of nearly �500), this is probably the most appropriate distance learning course for you:
http://www.nctj.com/distance_learning.php?ctyp ee=2&dist_id=dist_id
However, you can learn a great deal simply by getting some relevant books from your local library. If your writing is good enough, you won't need any qualifications. I started writing for the local newspaper at the age of 14. (You never forget your first byline!). I was getting occasional payments from magazines before I left school. I didn't bother taking a qualification until I was your age. I enjoyed the course but I've not made any more money out of journalism with a distinction certificate than I did without one.
If you enjoy writing, let your local rag see what you've got to offer. Just do it for the fun of it (and the thrill of seeing that first byline). You might make some money later on but don't get too disappointed if you don't.
Chris
(PS: When you send your work to the newspaper, make sure that you remind them to print your byline. Some newspapers aren't entirely ethical. I've seen an entire page of my writing, in the Sheffield Green'Un, printed under the byline of a staff writer, rather than my own.