Hi Miriam,
turning a blog into a business takes a lot of work. I was in a monthly Mentoring class held by a prominent blogger, Yaro Starak. Quite simply his recipe was to write lots of articles and post them and reach out to other bloggers with comments and trackbacks.
I think he's right although I don't think you need to write long articles, short posts can be fine. It just needs to be interesting!
What I need to do next is use my blogs more and learn a little about RSS and get an up to date Ping List.
BTW, I have a membership site and nearly everybody who has one will tell you about the time and energy spent on setting it up, adapting it, running it and so on. Basically a membership site is only a "wrapper" around a list.
I think your major job is to build traffic to your blog and get some regular earnings. Then what you do is to "rinse and repeat".
Nobody makes a real income from one blog-one blog may make you $200 a month or $50 or $500! You will need several and you do not know in advance which ones are really going to work. do not be surprised if even after carefull market research your blog does not earn much - just move on to your next one.
All The Best
Alex
PS I said "nobody makes a real income from one blog - of course the "celebrity" bloggers like Yaro Starak
http://www.entrepreneurs-journey.com/
and Steve Pavlina do
http://www.stevepavlina.com/
What most people are doing with their blogs is called niche marketing. You might be interested in an ebook by Andew Hansen called "Niche Marketing On Crack". Ghastly title but it's a good book!