I disagree with some of the above posts.
First you have to understand how the bank services their properties. Some local and community banks will do in house servicing and some banks and investors will contract a servicing company to do so. You have to deal with the correct party.
The notion that all these jobs are taken, frankly is hogwash. (sorry folks). I have repeatedly needed to hunt down new agents for our REO's because I wanted a new fresh firm to work with or we entered a new market, etc. There is a ton of opportunity if you look in the right place (even more if your good!).
The post above that said you have to be visible is true. And certainly each investor, servicer or bank will have their own criteria of what they want in an agent. The primary parameter, be good! Be on top of my assets, have a solid marketing plan and help manage and sell the property in a efficient manner. I always say, no one will care more about my assets than I do, but the REO agent should be a close second place.
As an agent, you can speak to local banks. You can also contact mortgage servicing companies and ask them for the REO department and ask how to get approved on their list. Most don't understand this is usually a 3rd party list supported by RES.net or LPS or some other of the same and is not in house.
Speaking from experience, you will only have one chance to impress remember to make the most of it. I as an investor have always been very hands on with your assets. When the investor or servicing asset manager calls and identifies him/her-self, treat that as important. When you get your assignments treat them as they were your own assets. I have terminated many relationships as firms get large and service levels drop.
Lastly, please know and understand what your asking to become. REO agents are a bit different. As an REO agent you need operating capital in most cases. All expenses are paid by the investor but you may have to fork out money upfront and payment from the investor or servicer may be net 45 days. You need to have contacts which trust to work with. Any sub-contracted service is a representation of you, if they fail, you fail. Also, have more than one option. Having one contract is great, but I want to see I am getting a fair deal, and I will request 3 quotes. Don't commingle services, if you are also the contractor, I usually will be mindful of being taken advantage of. Hope that adds some additional clarity.