At the start of a new site, it’s often times better to build value to the new site instead of trying to monetize from it immediately. A good example is YouTube. They’ve built quite the following and I’m sure at some point Google will start making big money off the site.
Here’s another example: As a programmer, it’s usually better to write your own scripts and sell them over and over again – instead of just doing custom script jobs for others.
A writer is better off writing for his own blog rather than writing guest posts for other peoples’ blogs.
In closing – building value and spending time on your own sites first is better in the long run than chasing the quick buck.