It's possible that his connections and encounters from his work as an agent formed the foundation of his 'book' - and being a real estate agent is like 99% about building that book and 1% about doing things the rest of us might refer to as "work". Many if not most of the successful agents I know are moonlighters for this very reason.
Not ragging on real estate agents, it's not an easy thing to pull off; convincing someone to hand you 3-6% of the biggest financial transaction they've ever made just for you to negotiate for what's probably a grand total of a few hours and do some online shopping. And they do provide value insofar as knowing the landscape can really help a client avoid getting bent over a barrel.
Source: did it myself (poorly, which is why I'm in tech).