Once again there is no such thing as a free lunch...unless you live in your parent's basement..then you're living like a king..lol mine away!
No but seriously yeah I bet most smart landlords do include a small clause or disclaimer that will prevent you from consuming the Gigawatts of electricity your dream mining farm would require. So I'm afraid with all things you gotta pay if you wanna play. Thankfully mining is still profitable - for some people - so the electricity costs can be covered and justified.
If its an apartment building without meters for each unit, it would be sorta hard to tell who's using all the electricity. I guess you could just start shutting down breakers and see when the meter slows down a bunch.