I don't think you should even concern yourself with that. Any COMPETENT electrician will know what to do if you tell him you need a dryer receptacle in the closet.
If I were you I would be the one to have the work done because you can hire a reputable EC. Then deduct it from the selling price. You DON'T want the building handy man doing it, as happens all too often because you know the seller isn't going to spend any money on it.
-Hal
