Look for Key Attributes in Collection Agency
You can hope you never need the services of a collection agency, but it's likely that you will. Suppose a resident skips out without paying the share of his rent above his subsidy. You are entitled to pursue the resident within legal means to collect past-due debts. That's when a good collection agency can be invaluable.
HUD could reimburse your loss from past-due debt, via a special damage claim, but first you must demonstrate that you have taken “all efforts to collect the debt.” Working with a collection agency can show you are making that effort.