well first off LED's are expensive. A 150 watt HPS goes for around 60-70 USD. There are also T5 fixtures. a 2 ft 2 lamp system costs about 60-70 USD also buts puts out 10k lumens as opposed to the HPS which puts out around 15k lumens. The T5 would be good in your situation though (and probably in any situation) because you can place it vertically rather than horizontally meaning its very flexible in terms of space management and you still get good light output, and also that they create barely any heat in comparison to the HID systems. Btw 150 watts is not really much electricity but idk your financial situation so i cant judge. THe t5's i talked about are i think 110 watts too just so you know, and ive heard great things about t5's.
Mylar (reflective paper type stuff) costs a dollar per sq ft, and 1 quart of flat white paints costs 8$ where i live. Just make sure if you decide to use paint that you you place a second coating of it.
I have seen excellent grows with CFL's. There is a thread on another MJ Forum (dunno if i can link it so I wont, but if i can, someone pls tell me cause it could help this guy a lot) where a guy grew about 22+ grams per plant with 46 actual watts of CFL in the most basic DWC Bubble system. If you ever come across that thread, you will be crying due its simplicity and the results of the plants. fastest grow i have ever seen and one of the healthiest. anyways...
you must be able to invest in a fan+carbon filter. Theres just no way you will keep this a secret without those two items. My plants are only 3 weeks into veg from seed and i can already detect the aroma of marijuana and pine. And thats only in veg.
If you want maximize your grow, you really need to invest in nutrients, otherwise you will have a grow that severely lacks in buds. Just my opinion, if youre gonna take the risk of growing pot, you might as well grow as much as you can. if your roommates find out they wont care how much pot is grwoing there, its still pot, and its being grown in their home. and if the popo discovers this somehow, well...