Being in college, I make nearly all of my money in the summer and then work just enough during the school year to scrape by until next summer. My lowest account balance is always right before my first big internship/co-op paycheck. Last year, that was $1.41, this year it was $35.63. I'm entirely comfortable in the tens, single digits less so. At least $10 will buy a week of food, if I'm careful with what I buy and how I eat it. It's pretty hard to eat on less than that though.
By the end of the current internship rotation I'll have several thousand dollars, all in the checking account because I can't risk it in investments. I could put it in a high-yield account or CDs or something, but that's quite a bit of work for what will net me a little over $10 before I need to take it back out again.