Hi Christine,
There are a range of rental properties available in Erbil. The most expensive ones, and the nicest ones, are in the new housing developments such as Naz City, English Village, Italian Village, Dream City, and others. You can find out about these by visiting the admin office located within the complex. Rents are very high, with most more than $2000/mo. Lease of one year is typical. Utilities are expensive, but reliable.
If the resident is Christian, he would want to consider the Ainkawa area, which is Christian. There are many properties available, not as nice as the ones mentioned above, but rent much lower. I am not sure how one goes about sourcing these properties. Must confirm utilities reliability at each location.
In addition, there are Rental Agencies who have a range of flats and apartments, with wide range in quality and price. One must be sure of utilities reliability when selecting one of these properties. Local residents can point you in the right direction for the Rental Agencies.