This is from a PGY I, starting in July.
There are 2 forms of moonlighting possible, in house and external. Not all institutions offer in house moonlighting, but mine, Carolinas, offers shifts in the fast track at $60/hour (10 hour shifts). You can do this as a first year, as long as you have completed 1 month of EM, and stay within the 80 hour work week. Other programs have things where you can teach ACLS, do code call, take admissions for other services,etc. All of these, as long as you are working under the auspices of your home institution, don't require you to get your own malpractice insurance. Nor do they require you to get a permanent medical license.
Now, on the other hand external moonlighting is quite different, because you are essentially going out on your own and working in an ED independent of your residency program. There is a big debate as to whether working independently in an ED while still being a resident compromises the validity of the specialty. I'll leave this alone. Anyway, there are certain requirements to being able to moonlight. 1) You need your permanent medical license. Thus, you must have completed 1 year of post graduate training and pass step 3. (This is different for FMG's and DO's in some states) 2) You will need seperate malpractice insurance. This is usually picked up by which ever institution you are working for. Getting your medical license is expensive, but well worth it when you are pulling in an extra 30,000 a year in some cases.
In addition, some programs use a cutoff for the inservice exam for moonlighting. It varies among programs. I hope this helps.