down on (one's) uppers
Having no money; broke. The phrase was originally used to describe people who were so poor that they had worn their shoes down to the uppers (the part of the shoe above the sole). I am down on my uppers this week, so can we go out for drinks next week, after I get paid?
down on his uppers
Needy; fallen on hard times. Men's shoes have two parts: the bottoms (soles and heels) and the uppers, which cover the foot. Someone whose financial condition was so bad that he couldn't afford to have the soles and heels replaced after being worn away was literally down on (in the sense of “to”) his uppers. A similar phrase is “down at the heels,” and moving higher, “out at the elbows.”