Most residencies pay around 30k with benefits. It may be different, but at IU you are required to do some research and write-up of publishable quality. You don't have to be at a certain class rank, but they do take GPA and boards scores into account.
Some positions are more competitive to get than others, but if you really want one, you can get one somewhere. There are places all over that don't match for a year. If you are willing to go anywhere, you can get one regardless of rank, GPA, etc....well with in reason of course.
This is very dependent unpon the year. There are several residencies that are always in high demand due to their reputation. For example, the Huntington WV VA hospital had 25 applicants for their 3 slots last year. Some other residencies didn't match at all or only had a few applicants.
If you are serious about a residency just do your best to keep your GPA and boards scores high.