We have several sites with AdSense on them, and they're doing well. But we'd also like to sell banner ad space to our users. Now we're going to write it from scratch, and do everything internally (except credit card payments). We're not partnering with another advertising provider. Is this against the AdSense TOS? If it is, should we replace the AdSense ads with banners if there's an appropriate banner, and display AdSense if not? Or do we have to drop AdSense alltogether? Thanks in advance
As the TOS says, it's only a violation if the other ads are triggered contextually or look just like Google ads.
Regular text links shouldn't be a problem, but whenever in doubt, it's always best to check the Adsense Terms of Service, and if you can't find your answer there, aks google directly.