Damn it, I wrote a long reply and closed the window before hitting submit. I'll try again, keeping it more brief this time and to the point.

You would never make money with any third party advertising networks. What I suggest you do is sell advertising through direct marketing.

Visit the websites of your competitors and make a list of companies that are currently advertising on these sites. Chances are they are on an active spending spree and looking to spend the allocated advertising budget effectively. Once you have the list ready, approach each of those companies on an one-on-one basis by introducing yourself, your website and by offering a long-term one-shot package at an attractive price that makes sense to you and will be appealing to them as well. Keep those emails personal, show knowledge about their product/service. Treat it as if you were applying for a job and had to submit a cover letter with your resume.

I followed this strategy with one of my websites and my conversion rate was 1 out of 7 emails sent (on average).