I agree with Bridie. When starting out with your business, so that you can give your clients the best possible service, you may want to consider offering only those services that you are highly skilled in.
If you have not transcribed a lot, follow Bridie's advice and sign up with a large transcription company to get yourself going. You will learn a lot, pick up your typing speed, and discover if you like it or not. Like Bridie, I love transcription. I love putting people's thoughts and their spoken words into written form. But it is a skill.
And then it all depends on the type of transcription you would do. If a client has simple letters or memos that he/she has dictated and wants them transcribed, yes, that is a piece of cake (most of the time). But if you are going to try to take on interviews, focus groups, etc., that might result in you giving up because those can be nearly impossible even for highly experienced transcribers.
So good luck -- and don't give up on your dreams. Be realistic though with what you can offer your clients and follow Bridie's advice. She has been doing this for a long time, and she knows what she's talking about!