I have 2 apartments next door to each other! one is doing really well, the other we have just opened for the season, is there anyway that potential guests will see the new apartment as an alternative if my original one is fully booked?
Now one scenario might be to add count to the rooms after adding pictures of the second unit and rooms.
So when booked you simply assign the second unit and the rooms via your messages to guest.
Otherwise add the apartment as a second listing. Its not clear above if you actually have already.
Perhaps share the property links.
Can also be added to your profile, click on my name to see a How To Guide.