You seem to imply multiple things with your assumptions Cheddar and Tom, not least of which is that buying and selling is only possible through an agent (so you either pay one, or you are one). This is not the case.
You can buy just fine without an agent, and you can sell without an agent (and you can use a listing service that list on the MLS for a flat fee, often only a few hundred dollars, no percent commission needed).
Further, a licence restricts you in certain ways, leading to many more disclosures, etc.
This is on top of the time to earn it, time to keep it up (ongoing classes and education) and the money it costs (initially and ongoing yearly licensing fees).
It's well worth paying an agent - IMO - to avoid those costs and hassles and time, and you'll probably even come out ahead dollar-wise.
Even if you have your license you still have to pay the agent of the other party (or the other side does, but either way it's less money you can make on the deal), so you're only saving one side of it, at best.
I'd personally be buying without an agent, then using an agent to list and sell it and pay their commission as well worth it.
If you're looking at doing this as a full time job or business, it's different. A side gig in ER? I'd definitely skip the license.