Hi! We own a 2 story 4 plex, that is currently a 3plex. We live on the 1st floor where 2 apartments have been joined opening up part of the wall between the 2 kitchens. We would like to do the ssame thing to the apartments upstairs. What do we need ot know before we do this? The downstairs apts. were joined when we moved in. I am not planning to make a large 'hole', incase someone would want to convert it back to 2 apts. in the future. I am pretty handy, but I haven't tackled anything like this before.