If cost is prohibitive try second hand as pahpah suggested, least for the expensive things like a light.
Craigslist, ebay ect.
You do not have to use LED.
HPS can be picked up dirt cheap these days.
BTW stagnant air in a room is not ideal.
Contrary to what some believe before starting this journey cannabis likes a climate not far from what we like.
You ideally want to be able to ventilate your room/grow space.
Anyway, things like lights, fans ect can be picked up second hand .
Tents , I would buy new but they are cheap enough.
Be wary or kits like the one you posted, as you can see they are selling you a reasonable tent, fan, filter ect but with a light not powerful enough to light half the tent.
Though it doesn't hurt to have more space than you want to fill.
Just run whatever set up you find by folks on here before buying.
Try not to run in head first.
Welcome to riu