The nice thing about podcasting is that it's cheap, easy and simple, and all he needs is passion on a particular subject. It's also best to go after a narrow audience instead of trying to get as many people. He also would need to have sufficient audio quality so it's not difficult for people to listen. Other than that, he just wants to communicate his deep knowledge on the subject and his passion for it. He shouldn't expect to make any money though, because that is very rare. He might not even cover his costs.
As far as tools for doing the show, he already has a laptop. He can use Skype for two people with Plantronics .Audio 655 headsets for $30. Then he'll need a place to store the shows, and Leo recommends Libsyn for that. It's $10-$15 a month. If he's got people all in the same room, then he'll need mics and a mixer for it. Behringer makes a podcast kit, but that's where things start to get expensive.