Here’s the thing you need to know: Google has no strict criteria for acceptance into the AdSense program, and AdSense doesn’t hit you with a minimum traffic requirement. The only criteria they’re really sticky about is the standard “acceptable content” requirements, and that’s pretty standard almost anywhere.
Google AdSense says they’re serious about attracting quality content sites, and because of that they only allow AdSense members to serve ads on pages with actual content on them (it can’t be a page of ONLY ads). They have a variety of ad styles from you to choose from, including banners and skyscrapers.(Note: banners are those horizontal ads that run up top and down bottom. Skyscrapers are the tall ads that run vertically, on the left or right of your page text.)
Once you’ve been accepted into Google AdSense, you’ll be able to get the AdSense advertisements on any site you own using the same ad code, provided you obey the Google guidelines. (And that’s very, very important—more on that later.)
Your reporting doesn’t occur in real time, but I’d say it’s pretty close. The stats are updated regularly throughout the day. You can also view reports based on a domain or site basis if you run the AdSense on more than one site.
Before you sign up, you really ought to read the lengthy and detailed FAQ on the AdSense site.