The blogs are mine gold if you work propertly.Most people say that this kind of CMS is much better indexed by Google.Completly wrong.A free site or a TGP isn't anymore difficult to get indexed than any other page. It all depends on its construction and who is linking to it, just like anything else.
Google doesn't care if you use WP,drupal or static pages. Inbound links, content and on-site optimization are what matters.
Wordpress are more SE friendly than most people can build simply because they don't know much about optimization.
Blogging takes patience and tons of it and time but in the long run you can build a network of blogs that can generate money.
A good advice is to start up with around 10 handwritten blogs and grow progressive.
Good luck
