You're joking right? There is no money in other events. Unless he wants to clean up on the US championship circuit, the most money is in the marathon - by far. It's not like he's going to be making money running 10,000s on the DL circuit.
The one problem is that he is probably most suited to half and 10k more though. Biomechanically suited to other things. He could probably make more money. Race more often and likely win more often too. I'd bet on him going sub 60 faster than him going sub 2:09