She has owned the house for decades. 
The townhouse is five stories tall; has a gargoyle-shaped door knocker; a two-car garage; a fountain; and is surrounded by a brick wall with two gates monitored by security cameras. The front door is also monitored by security cameras.
In the Radio Play, Demona brought Eddie Brock, John Jameson, Dominic Dracon, and Cletus Kasady to the townhouse after breaking them out of Ravencroft. After her thieves delivered the Spear of Destiny to her, she used it to restore Eddie to being Venom, Jameson to being Colonel Jupiter, and here she used Cletus Kasady to create Carnage.