I speak of those options because thats the way it was on some previous car forums which seemed to work out.
Vendors would pay whatever the fee was to be a featured vendor (usually wasnt a lot and was a one time deal). For that, they got their own section in the vendors area and a banner ad for the site, and now with the fact that ads expire over 14 days, it would be cool to make their ads unlimited. There was also a vendor only discussion section that regular members couldnt see (Im sure you have a moderator section similar) where they could talk about pricing, success with online sale, etc... whatever business people talk about. They could pool thier collective info together to help each other out.
Obviously if you have a long running member thats donated plenty, you can waive the vendor fee, but if someone new here wanted those business features then they would have to pay.
Once again, just a thought. Not sure how many of the current mods have been mods on other boards so not sure what everyones experience is. Just throwing out some past experience to try and help along the board.