Check the free adverts posted on the windows of grocers, chemists, snack bars and small restaurants, in universities, etc.
Consider a flat share.
Don’t hesitate to ask your co-workers, friends, etc., for help. Word of mouth travels quickly for these things.
In the case of an emergency, you can hire the services of estate agents, found in certain regions.
Note that there is no welfare support or aid for housing in Lebanon. Universities do not really have halls of residence and, when they do, these are reserved for the students of those universities.