I don't have one yet either. Would like it to be big enough for extractor, several supers to be extracted, a place for and hold cappings, a tank to put honey into, a sink and bar for filling jars, and possibly another room for cases of new jars, empty and full ones. Heating and airconditioning. The size would also have to fit your operation. Thought I had one, a used portable building, then the fellow backed out of selling it. Hope this helps and maybe someone else can give you a better idea.
Joe