I actually went ahead and made an immersion chiller with 25' of 3/8" copper. I used my hands and a copper bending tool to shape it and then soldered on 3/4" copper garden hose fittings. I used a spigot to run water through it and also threw the kettle in an ice bath as well. It took 16 mins. to cool about 4 gallons of wort (Russian Imperial Stout) to 65 degrees. From what I've read so far I think that's okay. However, I only saved about $15. Given the amount of time and effort it took to bend it without kinking it and the numerous trips to Lowe's to find just the right stuff, I would just buy one if I had to do it over again
I did gain valuable experience though and it works! Thanks for all the ideas!