Get a nice 600-watt HPS. Running 12 hours a day it only uses 216 kW hours per (30 day) month. Figure out what your electricity rate is. If it's 11 cents per, that's only $23.76.
Go to your landlord and tell him/her that you've just purchased a new computer - or plasma television but if they're ever in your apartment and don't see the plasma it would seem odd and I bet you've got a computer lol - and you've figured that at the amount of time you'll be using it each month it'll run your electricity up $23.76 (whatever) and just give him that much extra. He won't bat an eye except maybe to thank you and to gripe about the folks in 2C who must be running a small factory in their unit and thinking he won't notice the extra usage.
[EDIT: People hear about operations getting busted due to electrical usage and think, "Man, I better not even try," without realizing that those are cases where people have 15-30,000 watts of light, they get caught stealing electricity, or their "extra" usage is just one of many other suspicious things that are going on where any idiot walking past would say, "Hey, I bet they're growing pot in there."]