I need a classified ad script

I am looking for a classified ad script that bills the ad poster by % of sale. I would like to be able to set all ads to never expire as the ads get billed per sale. The script will need some type of admin, and mail to users to be preferably using smtp. The ad poster needs to be able to upload photos and multimedia to the ad. I also need something that is search engine freindly. If you have a pre-made script like this or want to mod one to do this please bid. Dont Bid If You do not have this script or cant produce one in a 2 days or so.