Hi Kiflom,
rental of a decent housing unit, a villa, though a bit far from city center, is possible for USD 400 to 600 a month. Apartment units in the city can be rent for 500 to 800 usd. Upscale housing rentals, villa, is in city (bole, old air port, etc) ranges from 3,000 to 5,000 usd,generally. Expect monthly groceries to run up to usd 500 for a family of 3. Annual gym expense for family is under usd 1,000. Annual Schooling, per child, the highest standard (ICS) is close to usd 20,000 per child but be sure to have a decent one for less than usd 2,500 annually. Current price of fuel- petrol- is close to usd 1 per litre.
Very general statement: For USD 2,500, one can lead a decent life with a fimily of 3 to 4.
Hope this helps.