Down at Heel: To be poor
Recorded in 1732 in William Darrell's A gentleman instructed in the conduct of a virtuous and happy life
Shoes and shoe leather were expensive, for the poor repairs were costly and as they often only had one pair of shoes, difficult to manage.
The phrase well heeled may have arisen as an antidote to this however there are other theories on the origin of that -
Louis XIV (1701) by Hyacinthe Rigaud (again).