Believe me blogging can evolve into a full time business if done correctly on right lines and consistently. All you have to do is to put your effort passionately. You can do blog posts related to any field, like technology, arts, or science etc.
Many young bloggers now a days earn 1000s of doolars monthly and I know many of them. This is because the worked consistently. They provide value and quality in thier content.
One thing more, you can adopt blogging as aprofession but, you should not write for money. What I want to say is that many bloggers now a days write only for search engines while forgetting that they have to provide value to thier visitors, so they may come again and again. I f you write for money then you will not develop trust of your vistors and they will tend not to come back.
Moreover if you write content only meant for crawlers then I bet that you can not succeed in long run because I think that google search engine has now evolved to a stage that you can now consider it as a human (in matter of judgement of quality), while working at super human speed.
This is because some people say that search engine is a machine and cannot judge quality of content, but this is totally wrong.