With a name like "Mistress Overdone," it's no surprise this character runs a brothel outside the city limits of Vienna. When she finds out that all the suburban brothels are being torn down, she's not happy about it: "Why, here's a change indeed in the commonwealth! / What shall become of me?" (1.2.100-101).
Maybe you know Mistress Overdone's famous colleague, Mistress Quickly from Henry IV Part 1 and Part 2? If so, then you've probably noticed a few similarities between Mistress Overdone and everybody's favorite hostess from the Boar's Head Tavern. Aside from the bawdy names and the fact that these characters have a lot of "social" experience, Quickly and Overdone both operate in the seedy underworlds of the plays, and neither one of them is ashamed about it.
Check out what Mistress Overdone says after learning that fornicators (like Claudio) will be punished by death under Angelo's governance:
Thus, what with the war, what with the sweat,
what with the gallows and what with poverty, I am
When Overdone complains she's losing all her customers to the war, bubonic plague, capital punishment, and a lousy economy we're reminded that, even though figures like Angelo and Isabella consider fornication immoral, characters like Mistress Overdone see it as an economic opportunity.
Yet, Overdone isn't a heartless businesswoman. As bawdy and unruly as she is, Overdone is also the kind of person who takes care of the illegitimate child whose been abandoned by Lucio and its prostitute mother:
Mistress Kate Keepdown was
with child by him in the Duke's time; he promised
her marriage. His child is a year and a quarter old
come Philip and Jacob. I have kept it myself, and see
how he goes about to abuse me. (3.2.200-204)