The factories and estates work the same way in that if you add a new property to your list, it will carry forward to all susequent months. You only have to add it once because all the pages refer to the one immediately before it to copy the information. So just as before, list all your beginning holdings in Ianuary. Then add any new purchases in the appropriate month as you go.

Remember if you run out of space to start opening up the hidden rows which allow you a good hundred lines or so to expand.