You are paid during residency. It looks like in the Chicago area, you can expect the pay to start around $39k / year. You can view the salaries for different programs at the
FREIDA website.
You have to do a residency to be board eligible in a field. After completing medical school, you can also just do 1 year of internship and obtain a license to practice medicine. I only know a very few people who have done this in recent years. All residencies I know of are at least 3 years, and can be as long as 6 years (neurosurgery for example). If you include general surgery plus vascular surgery fellowship, you could be looking at 7 years. I'm sure there are other combinations that can be longer.