Records of her business can be found as early as the 1870s, when she successfully appealed a verdict brought against her for operating a brothel. City Marshall Frank Touart had testified that "she took out a city license for a boarding house during my term of office" and that "during my time as City Marshal men were in the habit of visiting the house until very late hours of the night." However, her conviction was overturned due to "loose and unsatisfactory evidence upon which to convict a person of such an offense."
By the 1910s, McCoy owned several of the higher-quality bordello houses on the Zaragoza Street "Line," the most famous being Hazel at 15 West Zaragoza Street, a twenty-room brick house opulently decorated in baroque fashion, with Mollie's name in gilt lettering on the door. As described by Danton Walker, who played piano there before becoming a New York Daily News columnist, "The ceiling was high and windows floor length, masked by curtains of cherry colored satin; the walls were papered in gold and there were gilt chairs … a wood fire burned beneath a white marble mantel causing a lively sparkle among the crystal ornaments."
The prostitutes at McCoy's establishments, some of them from as far away as New Orleans and Louisville, were widely considered "the prettiest girls you ever saw." Mollie forbade them to walk the streets during evening hours or to drink, smoke or act indecently in the public rooms.
- Cases Argued and Adjudged in the Supreme Court of Florida During the Years 1878-9
- James R. McGovern. "'Sporting Life on the Line': Prostitution in Progressive Era Pensacola." Florida Historical Quarterly, Volume LIV, Number 2, October 1975.