Many agree content is the key. If you want to monetize your site, ads can't be all you find in the page. I personally feel comfortable with a decent amount of ads, among a decent amount of valuable content on topics I'm interested in.
That said, let's get back to webmaster seat. How many words are enough content for 1 page so you can generate new, fresh, interesting pages weekly? If you have to write 5000 words a day for 1 page, you probably won't earn much.
If you write 50 words, same thing because is not enough.
So what is a nice number? 500 per page? 300? 1000?