Pros
H&R Block does 3 months of training when you start. You can opt to do night classes where you will learn all about the tax code. It really is a great starting platform for anyone trying to break into tax. Another good thing is that since H&R Block is big they have clients who will come in the door and you'll get clients just for being there. They have a great training program that allows you to advance your skills up to a higher level and do more complex tax returns. You should definitely make an effort to advance as fast and as hard as possible so you can get more skills, pay and experience.
Cons
The starting pay isn't all that great. When I was working it was just $10 per hour. Afterwards, you'll get a commission on the returns that you do. The comissions themselves aren't all that fantastic, but it's still a great place to start.