In all honesty(I started real estate 5 years ago for the exact same reasons) I'm not sure it matters. Here's why:
1-If your goal is investment, would your time be better spent learning how to be an agent, or learning investment?
2-From personal experience at both National(Keller Williams) and no-name(City-Closers) brokerages, the only time the name of the company has cost me has been when speaking with luxury sellers. Even then though, most clients choose YOU, not the brokerage you work for.
YOU MUST KEEP THE END GOAL IN MIND OR YOU'LL GET LOST IN BEING AN AGENT AND WASTE TIME DOING THINGS THAT AREN'T BENEFICIAL TO YOUR END GOAL!
My best advice is to choose a brokerage that can help you with your goal as much as possible...If rentals/commercial real estate is the goal, then you're going to want to become a WIZARD at analyzing properties....I'd research commercial brokerages that have good training programs....it may be difficult at first, but at least you won't waste years.
Hope this helps!