New York (CNN Business) - As of noon today, Donald Trump is entitled to an annual pension of $221,400 and perks worth far more than that. It's possible - but not certain - he could lose that if he's convicted in the upcoming Senate impeachment trial. The law does not grant pension to presidents whose time in office ends through 'removal' by the impeachment process. Although Trump is still facing an impeachment trial in the Senate, a conviction cannot result in his removal from office since his term ended ahead of the trial. So, if the Senate convicts him, it would likely need a second vote to make Trump ineligible for his pension and benefits, according to Michael Gerhardt, law professor at the University of North Carolina. That second vote would remove him from the office of former president, resulting in his losing the benefits of that office, according to Gerhardt. But other experts question whether even a second vote would be able to strip him of the pension and perks. 'That seems pretty questionable,' said Demian Brady, director of research for the National Taxpayers Union Foundation, a government spending watchdog. Other benefits The other benefits Trump will receive, in addition to his pension, can be substantial - travel allowances, office space and staff salary can top $1 million annually for an ex-president. According to analysis by the National Taxpayers Union Foundation, since 2000 a total of $56 million in perks and benefits was provided to the four current living former presidents. Brady said one of the most expensive perks for ex-presidents is office space rent, which has no limits. Former Presidents Bill Clinton, George W. Bush and Barack Obama each had more than $500,000 in office rent covered last year, Brady said. Jimmy Carter's rent was only a fraction of that - $118,000. But that was still substantial. And Trump, whose businesses have billed US taxpayers more than $1 million for rent and other services since he took office, would be able to be compensated for rent for offices in his own property, according to Brady. One perk that Trump will not get that other former presidents receive is health insurance - a president needs to be in federal office for at least five years to get that perk, so neither Trump nor Carter qualify for that. Trump's wealth Perhaps the pension doesn't matter that much - Trump appears to have done fine without his presidential salary during his time in office. Trump and the White House have regularly announced that he gave back his $400,000 annual presidential salary to different government departments while in office. The law spelling out presidential pensions was passed in 1958, when Harry Truman, then one of two living ex-presidents, was experiencing financial problems. But there have been calls to end or reduce the pension and perks for ex-presidents, especially because most presidents today have significant earning potential from books and lectures. 'This law was originally enacted for a hard luck case. In the modern era these ex-presidents have such substantial earni