Just signed up for AdSense. I gave the url for the site I'm going to use it on, which already /has/ adsense ads on it, so we'll see what they say. If they have an issue, hopefully "I bought the site and am signing up for my own adsense account and will be swapping out the ad code soon" will be sufficient.
Huh. I composed this post this morning, and apparently forgot to post it.