The bubble feature will place the featured listings to the top. So not really the way to go if you want your listings in line with others.
From a Design perspective, what I've done was use [ISFEATURED] PLACE CONTENT HERE [/ISFEATURED]. All I did was just wrap a slogan like SPOTLIGHT! with a star, but I'm guessing you could get pretty fancy with those tokens if you wanted to.
As for selling featured only listings, I've not done it, but I've done some deep thinking on it. The only way I see that it may be possible is by creating a new DNN role then tie that role to the permission sets in Property Agent, and it should work.
What I'm looking at is creating specific roles for seperate PA instances like Classifieds, Autos, Jobs, etc, etc. Then I've created roles like "Salesperson, Dealer, Agent, Recruiter", and so on. Then I tie those roles to the PA permissions. By using Scotts subscription tools, a person could set up subscription to the roles for 3mo 6mo 1year, etc. Then do the same per instance of PA and have the properties locked on dates and expire based on the roles and subscriptions.
The bad thing is, you can only have each instance of PA tied to one expiration time for the whole module and not roles.
Hope I made sense!
Here's the featured token in action. Not very prominent (I gotta fix that) but you get the idea. Just look at where is say's "Spotlight". |