Photo: XNY/Star Max/Getty Images In the modern age, U.S. presidents can generally expect not to have to worry about money anymore once they leave the White House . They enjoy fat speaking fees, honorary gigs , and generous payments for their memoirs . But that rule may not be holding for the most recent ex-occupant of 1600 Pennsylvania Avenue: Multiple reports make clear that Joe Biden has had a different kind of experience over the past eight months. Rich people just don’t want to pony up for