Your best bet is probably going to be to find yourself a gender therapist. I don't know if you're in the US, but a lot of places here require a letter of approval from a therapist before giving anyone hormones. A therapist can also help you with finding trans friendly doctors who do HRT, and you can go from there. Cost varies greatly depending on whether you do gel, patches, shots, etc., and also where you order it from. Sometimes insurance will cover things, but usually not. Alternatively, some places do informed consent, so you could look into that as well. A therapist is a good place to start though, if you're just starting out.