Walmart sells this type tub for around 7 bucks:
If money is the main issue you can cool your wort with one of these with a small amount of ice and without keeping your pot open and without stirring during cooling to reduce risk of contamination. It works best if you can work outside and dont mind hefting your brewpot around (do at your own risk:cross
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Before I got a wort chiller what I would do was fill the tub part way with the hose then put my brewpot (with lid on) in the tub, then fill it the rest of the way until the pot was almost floating, obviously not so full that you risk getting hose water in your wort. Then wait about 5 minutes and the water in the tub will be hot, pull pot out, dump hot water and repeat. Wait about 10 minutes and the water is pretty warm, pull pot, dump warm water and fill a 3rd time adding your ice to the water this time.
By doing it this way I only needed to use maybe 8 lbs of ice and be at less than 70 degrees in half an hour or so. I could make this small amount of ice at home so saved on the cost of buying the ice and driving to the store to get it. Since then I've gotten a wort chiller which makes thing much easier mainly because I don't have to lug the heavy brewpot full of near boiling wort around.
The reason to only use ground water temp water for the first couple of baths is related to the physics/thermodynamics. Some of the engineers here could give you the formulas but the basic idea is the heat exchange from the pot to water bath is efficient when the temperature Delta (difference) between the bath and the wort is large so you don't need the ice because you are already on the steep portion of the heat exchange curve, and by dumping the water (which gets hot in a hurry) you are taking that energy out of the system. As the temp of the wort and the bath water get closer together (after dumping the tub for the second time) you are no longer on the steep part of the curve but you can again make the delta large by using ice water for the 3rd and final bath.
You see the same thing with a wort chiller btw. It works great in the winter, but in the summer the temp drops linearly from 212 down to 100 or so then drops much slower as you fall off the steep part of the curve. Thats why many have to use a pre-chiller with ice.
