About 10% of the agents do 90% of the real estate business. There's a cost to keeping the certification, including continuing education, etc. so if it's a hobby (selling a couple properties a year) it's basically a break even second job. The key is availability and the willingness to go show a property at 8am on a Sunday morning with a half hour notice - not always a possibility if on a trip. And then there's driving a couple around in your car for 2 months only for them to decide not to buy. My wife has a real estate license.