Hello,
You're 18 years old, so you should be of legal age to do all of this, if you have the money/insurance. This is what I did to get on hormones. This is a big step so take as much time as you need. It is however a long step so once you clear the hurdle of getting hormones you can just stay on the long plateau of hormones until you're ready for the next step, which for me was a legal name change.
Anyway, the first thing you need to do is find a licensed psychologist--not a therapist. A psychologist can write you letters that would be somewhat legally recognized. If possible, you should try to find a psychologist who specializes in gender issues, has treated patients with gender issues, or is at least open to working with you on gender issues. The best way to find a psychologist is, if you have insurance, to call that number on the back of your card. Follow the silly prompt till you get to a real person and then ask, "I need to know of some psychologists in my area that are covered, and I'd like to know what my coverage is for mental health." DO NOT MENTION GENDER LIKE EVER. You'll get a long list of doctors and numbers, so start calling. Ask the receptionist what you need to do to make an appointment and ask if the doctor has any history of working with gender/transgender. Once you get an appointment, you'll likely have a copay, the insurance will cover the rest. It may take a month or two, maybe three just to get in to see the doctor, but it is worth it.
Now, if you don't have insurance. All you can do is google psychologists in your area and go from there. Just be aware, they may reject you just for lack of insurance or you may have to pay the full price--like $300/hr. Some doctors have sliding scales where you can pay based on your income, but I sure never found any.
After a few appointments with a psychologist repeat the above steps but with an endocrinologist.
At some point, you should receive or ask for a letter from your psychologist that says that he or she supports your decisions, finds you mentally sane, and approves of hormone therapy under the guidance of an endocrinologist. My endo actually could have cared less about a letter from a shrink. She was willing to treat me with whatever I saw fit. You might be able to skip the whole first part in this case. Maybe just find a therapist instead to sort out your mental issues and thoughts. But ultimately, you will need a psychologist for surgeries so its a good idea to get one soon who can kinda oversee your whole journey.
After a few appointments with an endo, some blood test, you should be approved for hormones. As for cost here, it can vary depending upon insurance or not. Without any insurance at all, start up cost is about $1300 +$50-60 per month for hormones after that.
This is what I did. I'm nine months into coming out, and six months into hormones. It is an amazng process filled with so much emotion. I wish you the best of luck. If you have any questions feel free to ask me.
