Trump biographer David Cay Johnston outlines the president's greatest fears with Democrats investigating him

With news that the Trump Organization will soon be under investigation by the new Democratic majority in the House of Representatives, a biographer who's researched the president's finances for years outlined exactly what he has to be afraid of.

"Inflows of money from Russian mobsters and other criminal elements" are likely to be chief among Trump's concerns, biographer David Cay Johnston told CNN's John Berman on Wednesday night.

"Donald has long done business with these people and allowed them to purchase apartments from him through anonymous wealth corporations," Johnston said.

The biographer provided an example: "If you had a desire to buy a Trump Tower apartment in the name of Snow, Inc., Donald didn't ask, 'gee, is that a ski lodge in Colorado or a cocaine trafficking business?' He just said, pay up and I'll be glad to sell you the apartment."

Investigators hired by Democrats in the House are also likely to look for accounting books and records because "Donald has a long, well-documented history of hiding and destroying accounting records that were sought during audits."

Johnston added that although the Trump Organization has until recent years been a tight ship, the cooperation of insiders like the president's former attorney Michael Cohen and Trump Org CFO Allen Weisselberg with prosecutors could also spell trouble.

With Cohen and Weisselberg's cooperation, prosecutors may soon learn if Trump "took improper income tax deductions [and] whether he violated the Foreign Corrupt Practices Act."

They may also be able to solve "the unanswered questions about how much, if any, of the $10 billion stolen in Kazakhstan ended up with Donald Trump."

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