I surprised op hasn't asked, "how much do you think, I'll yield?"... Either way 5000w is a lot for a apartment. You said 5000w hps so I'm assuming this is just your flower room, So what are you going to run for veg? You know you'll have to runs inline fans for ventilation, ac if sealed room plus dehus. If this is your 1st grow, which I think it could because your going online to ask, "what will my electric bill be?" you're in way over your head. Also keep in mind you live in apt building which other people live, maybe some with kids. Keep that in mind before you go and blow out some room with crazy amounts of watts putting their lives at risk if there is old faulty wiring. These types of posts really rub the wrong way. Sorry and good luck.