In your first year or two, don't worry so much about commission splits - focus on who will give you the most training. Alot of real estate can be trial and error in the learning process. Read all you can - daily - because changes are happening all the time - new requirements, new disclosures, etc. Take relevant classes beyond your "required mandatory" classes. After a few years, you'll know when you REALLY feel comfortable in working transactions.
I was with two different national franchises - learned what I could, and, learned alot on my own. When it came to where I was learning more on my own and STILL craving more (and always will), I knew I was then ready to go out on my own.
One excellent place to learn about the mistakes NOT to make is to go to your state board's website. See if they post confirmed violations on the website. Virginia's board has the violations with a short transcript - it's extremely interesting reading and a HUGE educational tool.
Get the education - the additional dollars will come later.
Good luck to you!