Fannie Mae-No Politics (FNMA)

[Wise Man]

Lie. Warren Buffett didn't try to buy FNMA but its tax credits.

Warren Buffett's Berkshire Hathaway Inc. has joined Goldman Sachs Group Inc. in the investment bank's bid to buy $3 billion in tax credits from government-owned mortgage giant Fannie Mae, according to people familiar with the matter.

Source.
The Treasury Department blocked the deal.
So, he tried to profit off Fannie Mae when it was in trouble and not the other way around as stated in "gurufocus":

He said he probably cost Berkshire Hathaway at least $5 billion by not buying Federal National Mortgage Association (also known as Fannie Mae) (FNMA, Financial) 20 years ago when it was in trouble.

Buffett is known for investing only if there are government guarantees attached and in crisis (famous 2008 letter to his "friend" Hank Paulson, requesting Public-Private Partnerships)