Hello AgentVermont, welcome to Susan's!
Lots of good news and planning on your part - sounds like you have a great network of friends. My first therapist meeting was May 2017 with HRT two months later - my endocrinologist had a waitlist. If your therapist is good you have absolutely nothing to worry about. They should put you at ease, be totally open to your questions, and provide advice based on their professional experience.
I am sorry to hear your parents won't be open to your identity or sexuality. Or they might not be. Or... maybe they will be? There is only one way to find out for certain. Since you're in a situation where this doesn't risk your safety (they can't throw you out of the house), well you can see where i'm going with this. One reason is I had convinced myself my parents would completely freak out and reject me for the rest of their lives. That fear built up over time until I realized: if they accept me or at least tolerate this, wouldn't that be great? If they reject me because they misunderstand - or worse because they care more about what their neighbors think than about my existence, well then I've learned an important fact about them. And it turned out when
I came out to my 86 year old parents - I was shocked by how immediately and completely they accepted me. My mother is excited, and my father picked my new middle name. It's the female form of his middle name.
Life can be very interesting. All the best wishes for you.
Kendra