THE CONTENT - There are many types of "Adsense Ready Websites" out there and it may seem hard to figure out which ones are worth it and which ones are not. With prices ranging from $9 for 100 sites upwards of hundreds even thousands of dollars just for one. You might think to yourself, "wow what a good deal I'll buy the 100 sites for $9". Not really the wisest choice... As the old saying goes, "You get what you pay for". Those packs are usually comprised of the same exact content sold to every customer. (Static Content - never changing) Resulting in search engines to completely blow off your website instantly. There are already thousands of the exact same websites you are trying to submit. To avoid this situation you need to find a website that automatically updates their articles (Dynamic Content - constantly changing by itself) and the even better even rarer no duplicate content sites.
THE LOOKS - Some "Adsense Ready Websites" are very dry with plain text and no images in hopes of better ranking but this will actually hurt rankings a bit. There is no chance to name your image one of your target keywords.
Some make the sites look ok and few make them look really good. However, pre-made designs tend to be duplicated a lot. While humans notice this, the search engines do not. All search engines see is the image name and the alt tag. So if two sites have the exact same look but different content the search engines see two completely different websites.
THE CONTROL - Surprisingly the majority of "Adsense Ready Websites" make it difficult to insert your affiliate codes and make changes to the site if you aren't proficient with HTML. Some may offer software that will change the websites code on your PC so you can upload it to your server. There are a few that all you need to do is enter your domain name and the website is automatically created and hosted. The better of them also provide a web accessible control panel to manage aspects of your website in real time.
UNREALISTIC EXPECTATIONS - Although some are better than others you can get results with what you are given. While some make it less work and less time there is no magic bullet. Do not purchase an "Adsense Ready Website" and just expect the money to start rolling in. (Unless you get a good expired domain). For starters Google places new websites in their sandbox for a good 3 months. (Can be avoided completely by getting a good expired domain) No matter how great the website is it ALWAYS takes a bit of marketing elbow grease to get them moving along to big profits.