What is Google’s Sandbox?
There is no actual sandbox – there is no fixed time where Google does not rank your content. But … there are a number of ranking signals that prevent new sites from ranking. This is why some sites with lots of early content, social signals and traffic, good user interaction and high authority backlinks might start ranking well in as little as four months. These quick ranking sites have a staff to make all of these things happen. A more typical affiliate or ad-based content site take more time to get content created and get backlinks. They will therefor need more time to get past the new site ranking signals.
Keyword research allows you to tacticly choose a niche and plan your content marketing strategy. By focusing on low competition keywords in the beginning you get early ranking wins and build authority with Google.
By starting with an aged site you have at least a 6-month jump start on your online business. If you start with a revenue producing site you save a year or more.
Content is your product. It is what brings you visitors who you can convert to affiliate sales. You need to not only create compelling content but market it via your email and social channels.