So the layout and furniture in your condo are saved in a file that you can copy/paste and move around without much of an issue, right? Would anything happen if you got a condo file from another player with more belongings set down, and then dropped it where yours goes? Sorry if I sound dumb, I have no clue how the inner workings of this game function.
Id assume that the file is simply saying where what item has to be, and if you dont have said item nothing will be placed, and if the reverse happens where you got an item but the file dosen’t have an entry of where to place it it will just stay in your inventory, since items are saved on their servers, otherwise it would be pretty easy to mass duplicate items.
You can swap condo files. If you do not have an item that is present in that condo file, it will not be placed down.
So, in the event that you and your friend have the exact same items and the exact same number of items, you’ll be able to swap them around, otherwise the items you don’t own will not be there.