There is another possibility and I noted it earlier. Think Progress has details here:
http://thinkprogress.org/politics/2006/06/15/5792/hastert-pictures-of-corruption/
Hastert had steered a federal highway contract for Illinois through Congress and it just HAPPENED to follow a route that transected a big parcel of land he had invested in. I believe he wound up selling that for a nice bundle (TP says at least $1.5 million)…and stuff like that (which might not have been the only such scheme he was involved with - lots of folks would love to win favors from the Congressman and once you’ve done one, why not more) plus all of the money he likely made in the lobbying business, gave him the means to pay for what looks like blackmail. Sex, money laundering, kickbacks, political favors. There are many many possibilities Mr. Hastert might have been involved in, and as Speaker of the House, he obviously was in the right position to take advantage if he so chose.