I think that if you are hesitant about it maybe you can arrange to meet with a few practicing therapists to talk with them about their jobs and what it is all about. Maybe, I don't know if you can do this due to privacy issues, but maybe you could even volunteer in a therapists office. You would be able to get to know the type of people and environment you would be working in.

You sound very determined and if your mother does not approve of it now than she will when she sees it makes you happy.