How much can you make with 100,000?
If you are just throwing up a generic banner ad network, it's probably close to $.10-.25 CPM. Then multiply by how many ad units displayed per page (networks usually don't allow any more than 2-3).
So: 100,000 * .00025 = $25; x3 = $75
Very rough estimates. With a site with such a particular niche, he can probably get a higher CPM. I also count 7 ads on the home page.