Units and rooms are cleaned when the previous person moves out by either an onsite cleaning personnel or a hired cleaning crew. Remember that in your lease you most likely agreed to a unit with normal wear and tear, which has been cleaned for you to meet the office standards. This allows for varied interpretation of the cleanliness of rooms. Also remember that if that unit was cleaned a few months ago and you are the first one occupying it, there may be some touch up cleaning necessary. You may want to ask the office if you are allowed to view your unit before moving in so you can decide if any spot cleaning is necessary.