Being the leader of the free world is an expensive proposition. But the costs don't stop once you leave the White House. The nonpartisan Congressional Research Service says the federal government spent nearly $3.7 million on former presidents last year. That covers a $200,000 pension, compensation and benefits for office staff, and other costs like travel, office space and postage. The costliest former president? George W. Bush, who clocked in at just over $1.3 million. That includes almost $400,000 for 8,000 square feet of office space and $85,000 in telephone costs. President Bill Clinton came in second at just under $1 million, followed by George H.W. Bush at nearly $850,000. Costs for Jimmy Carter, the only other living former president, came in at about $500,000.