Congratulations on your health! Very, very happy for you! :D
But i have to say, you have a kindred spirit. When it comes to contortion I. AM. EQUALLY. OBSESSED! Particularly back bending.
A lot of the places that i looked up said that the cut off for contortion training is in the 20's, so starting now is a good decision and a must if you want to do it, but don't think its too late!
So long as you practice, You'll surprised how fast you get flexible.
I started training, very lightly, at sixteen.
I didnt have any formal training ether, so i used the internet mostly. You'd be surprised how many people do this actually. Its no substitute to having someone there to help you, but if your doing it because you WANT to do it rather than to perform, its probably the only sensible option.
As to what kind of stretches you should do really depends on what kind of contortion you want to do. Back bending, front bending, and so on. And the internet is great for looking up really any kind of exercise. Personally, i started with this site
link, but im sure that there are tons more that are probably better.
Unfortunately, one downside of teaching yourself is that you have to keep yourself motivated to practice. You have to practice at least once every other day to make any huge progress. I haven't been keeping up with it as much as i used to, so i can only get my feet to a little bit past my ears and i can pretty much do a split. Which isnt nearly where i was when i was practicing every day, but its still MILES ahead of where I was when i was starting. I couldn't even touch my toes when i began ^^;
One thing that you could do, especially if you want to start light and keep up with a good exercise schedule, is to start taking yoga. Contortion is basically extreme yoga, so taking classes is probably one of the best ways to keep yourself focused. That and you probably have someone there to help you if your doing something wrong or hurt yourself. It would also help avoid something that i ran into alot. Headaches. You need to BREATHE when you stretch, otherwise you can get wicked headaches. Yoga's good at drilling breathing techniques in early XD I know telling you to breathe is sort of silly, but you'd be surprised how hard it is to remember to breath when you bend. But if you cant afford it, the internet is FREEE! X3
And water! Drink water and eat! If you have low blood pressure like i do, back-bending too fast can make the blood rush to your head and you may pass out. That's happened to me a few times.
Ether way, its a lot of hard work, but if your really passionate about it, its worth it. You'll be able to do it and be really successful at it so long as you keep up with it.