Becoming a HUD approved listing broker is no small feat. I've put together a list of the steps you'll want to take if you are interested in becoming HUD certified.
Step One: Read through this website: http://portal.hud.gov/portal/page/portal/HUD/groups/brokers
Step Two: Then browse through here: http://www.hud.gov/offices/hsg/sfh/reo/hwtosell.cfm
Step Four: After filling in the required applications you will receive a HUD-issued name and address identification number (NAID)
Step Five: Find the companies that have HUD contracts in your state and then sign up with each of the companies you want to provide your services for to list HUD homes. Check this out: http://www.hud.gov/offices/hsg/sfh/reo/mm/mm3map.pdf