I'm about to start my last semester of school, and my plan was to be homeless for a lot of the same reasons you state. I started my homeless stint a week ago, and I already gave up. I couldn't handle it. I didn't have any problems staying occupied (12 hours/day at the library grinding 2+2 and SC2), but the hardest part was sleeping. Not having a normal, comfortable place to sleep was miserable. I either slept in my truck or on a bench on campus, and I don't think I ever slept for more than 3.5 consecutive hours. It is just way too hot to sleep in a vehicle and I couldn't relax outside with all the lights/noise/scary Mexicans walking around. If you have a friend's place to crash at at night then you might be fine. But sleeping outside will get old fast.
I think your cut in expenses is a little drastic. Instead of going from paying a lot of rent money to being homeless, why don't you just get a ****ty apartment for half the price or find a roommate on craigslist or something? Being homeless isn't going to help you develop discipline. I mean you might get more accomplished out of boredom, but if you are a good-for-nothing pothead now, you are just going to be a homeless good-for-nothing pothead in the future.
yeah i think sleeping in 100 degree weather without a plan for a shower and trying to go to work the next day might be impractical... i'll probably just be sleeping on the floor of a 1 br with 2 other guys, 1 schizophrenic :-)