Having sponsors for your blog or your blog post as an extra source of recurring monthly income?

Update:
You will have a set price for your blog or webpage depending on factors such as traffic, page rank, etc. For a sponsored post a small banner will either be above or below your post with something like "This post was brought to you by ....." or "This post was sponsored by ......"

If the whole site is being sponsored, then a button will appear on the front page.

Something like that. Its just an idea, but i kinda want some feedback.