Up-sell of other properties

Would be nice to be able to upsell other properties in the inventory. We have a number of properties that are available as additional space.

For example, we have a 3 bedroom lake property that guests often fill up, and we could offer them the smaller cabins if they want more bedrooms and bathroom. Ie. If you rent this property, you can rent these other properties if they are availble at a discounted rate.