James Monroe
As a politician in a fledgling country, Monroe was not always compensated for his service. During his time as president, he often paid expenses out of his own pocket, including some of the cost of rebuilding the White House after it was burned down by the British.
He left office in serious debt.
In the ensuing years, Monroe campaigned for back pay from the government. In the end, Congress provided some of the money owed, and Monroe was able to leave his children an inheritance when he died in 1831.