You can make a Plugin if possible to compare Listings as a user may always look at multiple Ads before they make their final decision. I know user can ad items to favorite and individually check each ad. But having a comparison plugin will help user a lot to compare products side by side from same category and also you may ad extra feature of saving items to compare later means a user can have one group for cars, one for property which they can compare without removing their existing items from compare list. I am not sure if its possible to have more than one group at same time but if its possible then that would be convenient for end user when they are looking at more than 1 product at same time.