It depends on what it is. Rope and duct tape can be in a utility room or in a kitchen drawer, and no one would give it a second thought. Hand and leg cuffs can be explained away by saying you're in to magic and escapes.
Some of the more "kinky" things, like ball gags, would be better buried somewhere behind a dresser, or in the aforementioned utility room or storage room, inside a locked footlocker or suitcase, to be brought out only when you have a session.
The thing you have to ask yourself, is "What can I leave out in the open, without it drawing attention?" Or, to coin a phrase, "What can I hide in plain sight?"