To start you could take cases that are simple tax returns typical of a single or married couple that have jobs but little in the way of investments and part time businesses.
A great way to get going once you have taken a course is to work for another tax preparer to gain experience and have a good source of advice.
None of this is rocket science and almost anyone who applies can do it. You'll be saving your own tax prep fees, and if you do a few for a normal fee you may pay for the course in the first tax season.
The bonus is that you will be better able to find your own tax advantages and opportunities.