Inductive coupling to only the neutral wire might be safe (if you can verify that the outlets are wired correctly).
It's probably not a good idea, however, not only from a safety standpoint, but because house wiring will crosstalk to other wires in the same building, at least back to the breaker box and more likely all the way back to the service transformer -- and thus couple in all the noise generators all your neighbors use. Small appliances. Wall wart power supplies. Cordless phones. Etc. You won't be happy with the reception you get, and there's also a strong possibility you'll generate interference on neighbors' TVs, radios and telephones (since, in effect, your antenna will be in their apartments).
Since you have a balcony, a 2 m vertical is simplicity itself to put up, and it's small and not very noticeable. For 6 m, a quarter wave vertical is still only about five feet, and even a 12 m quarter wave is just about ten feet. This is still a size that could pass as a flagpole, and has in many restricted locations.