Separate advertisers from site/community

I have a buddypress/multisite using Classifieds. I want to offer advertising through the Classifieds, so that advertisers can place an ad on a site. However I want to keep the advertisers out of the community. So I imagine a page where they can submit and pay for an ad (that will need approval by moderator), but that is that. Easy to do?

(Also, I have the payment option selected, but at no point does it ask for payment. Is this a setting that I am missing?)

Thanks