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President-elect Joe Biden is headed to the White House for the second time.
A good chunk of the Bidens' wealth also comes from speaking engagements.
Jill Biden was also reported to have made $700,000 in her own speaking engagements.
Former presidents have also raked in hefty sums from penning memoirs.
However, when Obama entered the presidential race, its sales skyrocketed.
In 2012, CNN reported that book sales were still the Obamas' main source of income.
