I was a keyholder for 3 cafes I worked at, either opening shift manager or closing shift manager. It was fun, but sometimes stressful. At one point I worked two cafes, one opening, one closing, and was at work from 5:30AM until 11:30pm 6-7 days a week for a whole summer. I got some symptoms carpel tunnel syndrome from the palm of my hand up the inside of my arm to my elbow, and screwed up my shoulder and lower back due to bad ergonomics (too tall for counters). <br />
One place I worked, I got a cup of water splashed in my face over nothing. Lots of rudeness, but lots of awesome regulars that turn into genuine friends, also.
I have changed jobs. I have some medical liability right now that keeps me from working a physically-oriented job. Once I get a clean bill of health, I may consider getting back into the industry. I think I'd rather try working at a roastery the next time around, though. The smell of roasting coffee beans is divine!
I did not own the cafes I managed. Shift-management wasn't particluarly well-paid, either - I made just about $12/hr, which in my area was bordering on the poverty line, hence taking the second job and working 80 hours a week. I was a highschool dropout, got a GED, and did not go to uni. If you end up deciding to drop out of uni, I suggest looking into the Open Courseware Consortium, Uncollege.org, Coursera.org, and degreed.com in order to supplement your education for free.