I moonlight doing admissions for our hospitalist group. Shifts are pretty open to what you want to do: days, nights, or some intermittent evening half-shifts. Money is pretty good and I've averaged one admission an hour which is super doable. I typically do 3-4 shifts per month.
It seems like the main opportunities for medicine residents are working for a hospitalist group, in an urgent care, or in an ED. ED seems to pay the best, followed by inpatient, followed by urgent care. There are probably other opportunities out there.
Every set up will have different pros and cons. I have a friend that works in a rural urgent care that pays better than the urgent cares here in the city and reimbursed for travel time.
The big thing is to start the process early, especially if you are planning to work in an ED or in an inpatient setting. Take step/level 3 early. Work on your state license and credentialling as soon as possible. I took level 3 in December of my second year, got my results in February. Then I put off starting the state licensure process until April...it took until July. Credentialling at the hospital took from July to November.