Franklin Raines is joining forces with Steve Case on a healthcare venture.

NEW YORK (CNN/Money) - Franklin D. Raines, former chairman and chief executive of mortgage giant Fannie Mae, is joining Revolution LLC, a Washington, D.C.-based holding company launched last month by former America Online chairman Steve Case, the Washington Post reported Tuesday.

Raines will act as an unpaid "informal adviser" to the healthcare investment firm, the paper said. When it formally launches its healthcare vehicle later this month, Raines will become an investor and a board member, it added.

Raines was forced to resign from Fannie Mae (Research) in December after federal regulators concluded that Fannie executives had misapplied accounting rules. So far, no charges have been directly brought against Raines.

However, the situation prompted widespread criticism since the accounting changes at issue allowed the company to meet profit targets and in turn triggered multimillion-dollar bonuses for various executives at the company.

Case and Raines have known each other since at least the late 1990s, when Raines joined the board of AOL after serving as director of the Office of Management and Budget in the Clinton administration. Raines stayed on the board following the 2001 merger between AOL and Time Warner (Research), the parent of CNN/Money. Case stepped down in 2003; Raines left the Time Warner board in 2004.

Raines has also served on the boards of Pfizer Inc., PepsiCo and TIAA-CREF.

After Raines' departure from Fannie Mae, Case invited him to work out of Revolution's offices, the Post reported, citing a company spokeswoman.

The Post said Raines didn't return a voicemail left at his office.

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