I'm starting to like that school bell.

The intro by Slash gave me hope he had clicked with the song. I don't know if he's just lazy or past it.

If you want to check costs here is a list of essentials with estimates:

Light 4-600W for a 4x4, scale it down for a 2x4 etc. ($100-1000). 

125mm exhaust fan for a 4x4. ($50-150) If it sucks in the walls on your tent at maximum power you have negative pressure and no smell will escape. Depending on the size of the room you're in that will even apply when you open the door to the tent. You can vent into the room but getting the air outside or at least to another part in the house/apartment is much preferable. Mature plants do produce a fair amount of moisture and you don't really want that in in your room/house.
If you vent outside be aware there may be carbon filter smell which a trained nose might take for what it is. Activated carbon smells sweet. If discovery is a potential problem you really want to control smell and where it goes. It won't reek if done right but keep as much distance to potentials as you can.

carbon filter ($100-200) better filter less smell. If you can get the best, get the best.

tent ($75-150) go for the cheapest you can find as long as it's a designated grow tent. Brands like gorilla grow got infared shielding and shit in the material which adds who knows how much to the prize. Yeah you're not going to need that. If there are light leaks just use some ducttape.

pots ($10-20) any one will do

soil/coco/dwc (additional cost maybe $100-300 for hydroponic setup)

humidity and temperature meter ($10-50) remember to make sure the humidity meter is accurate. Lots of bogus products out there.

ec/ppm meter for measuring nutrient solution ($20-100) digital is the way to go here

nutes ($50-100) (maybe a lot cheaper if you just go for generic solutions)

garden scissors ($5)

light timer ($5-10) go for mechanical

sunglasses or designated grow glasses ($10-20) when working in the tent

The absolute cheapest alternative are fluorescent lights you get at the tool store or whatever. As long as the wattage is there you are golden. Never mind all the talk about light spectrum, it's nerd talk with little real significance. I would however recommend going on the high side if you use those type of lights. They also have the advantage of running cool like the leds.
600W should be perfect for a 4x4, alternatively half that for a 2x4.

I would not recommend going with a bigger tent than 4x4 for a first timer. If you want a discreet closet a 2x4 is where it starts to feel smallish.

optional but very helpful if you want to optimalize yield
light meter to measure exactly how much light your plants are getting ($500)

Light is everything to a proper grow. Once you saturate light only more space will enable you to increase yield. The case I know about got exactly the same yield from 4 plants as it did 5 with everything else being equal. If you want the easiest experience you have just one plant, or two to hedge your bets, then you top it until the canopy is filled. Will take a little bit longer than germinating a bunch of seeds and caring for a bunch of plants, but you will still get a similar yield. You can use a net to space out your plant but I recommend tying it up for better control. Don't be afraid to do it early and keep doing it. Topping and bending. Don't be afraid to aggressively remove leaves so your bud gets more light. The goal is to get a nice even canopy with very little beneath.

Total $500-2000 ($2500)

With a 1000W led you should have had more than enough light. Did you measure it? Investing in a good PAR meter or what they are called is one of the best investments you can make. Will cost you 4-500 though. Canopy should have an even ppfd of 600 for veg and 900 for flower. And this was done in soil.

A 500W is enough and the temps will be around 26-27 degrees. You can get at least 25 ounces dry.