Police in Lethbridge say officers became aware earlier this month that the girl was leading a high-risk lifestyle.
An investigation determined the teen had been instructed by a male acquaintance to prostitute herself and give him the money.
Police allege she had a sexual encounter with a man last week as a result.
"This is a 13-year-old girl that was out working. It's very disturbing that's occurring in our city," Insp. Bill Kaye said Friday.
"Prostitution occurs on a regular basis. This is the first time that I'm aware of a girl this young working in our downtown."
Memphis Mathew Gros Ventre Boy, 32, is charged with procuring prostitution and is to appear in court next Wednesday.
Robert John Gerard, 61, faces several charges, including sexual assault and sexual interference, and is to appear in court March 1.
Both men have been released on strict conditions that include not having contact with the girl.
She does not face charges and police are working with social agencies to help her.