Depends on the niche. Have a look and see what typical keywords you expect to wind up on your site garner on AdWords; if you can attract eyeballs for less than, say, 40% of that price (to allow for Google's margins) – including your time or cost for content generation – then you might make some money.
But you'll need quite a lot of traffic in a reasonably high-purchasing-intent niche.
But you'll need quite a lot of traffic in a reasonably high-purchasing-intent niche.