There isn't much you can do (clinically) with just 1 year of training. And in all honesty, someone with just 1 year of training isn't really qualified to practice in today's world. Some states won't let you get a license without 2 or more years of training either, though there are several where you can get one.
Usually people just get moonlighting jobs in their residency programs once they get their licenses. Most urgent cares, doc in the boxes, or hospitals would never ever hire someone who didn't finish some kind of residency. It's just not legally viable for them...if you screw up and they get sued, they don't have a leg to stand on. They would be better off hiring a "board certified" NP or PA, who is "fully trained" and can do basically what someone with just an intern year could do, and would be paid the same or less.
One very important point to consider is that many, many insurance companies will not pay a doctor, and most hospitals won't credential one, who hasn't finished a residency. In fact, many insurance companies and many medical practices won't hire someone who isn't "board eligible" (meaning you finished residency and are getting read to take your specialty exam, such as the American Board of Internal Med certifying exam). It's hard to get a job without being "board certified" much less without even finishing a residency.
I think quitting residency is a VERY BAD idea in most cases, unless you plan on no sort of clinical career whatsoever. Taking a year off to do research or something, and/or switching residencies after an intern year is a better plan. Really one shouldn't quit any job/career without a concrete plan of what to do next.
A person could do an MPH with no residency, or do an MBA (with or without doing an internship) and then do something nonclinical. There are a few areas you can switch/get in to with just an internship to start. I heard that one can do sleep medicine, but I don't personally know any sleep medicine docs. I think you can also do a preventive medicine residency, which I think is 1-2 years after internship...that's usually for more public health type jobs with less direct patient contact, I think. You could check out some of those areas.