I actually write books that I sell on Kindle. To grow that income further I also built micro sites targeting relevant long tail key words.
As my business has grown I have scaled my core websites significantly and pretty much outsource everything.
But to start with, hands down, a wordpress blog is the best way to go as Google loves them as niche sites and ranks them very highly if you set them up correctly.
The single most important part is the keyword you target and the LSI keywords. The rest is just the process of creating a site and it's social pings and links. Do that properly and you can easily create a site a day, that after a few weeks should be making you $300+ per month on auto pilot.
Personally, as these are so easy to create, you should be looking to do the first yourself. It is a lot easier and better if you understand HOW you make money BEFORE you outsource. That way you do not become a slave to the outsourcer and you can scale when you want.
You should also be aware for a variety of reasons, not least the Google sandbox, not everyone of the micro sites you create will work.