[Mitchella]

For me the problem is not so much the lack of targeting the ads for the business but instead the traffic you'll receive. Lets say you call some businesses in your area and they jump on board since it's a dollar, very little to lose if it doesn't produce any results, perhaps 10 of these businesses decide to do it and 10 more randomly from the internet(most of which will be spammers trying to get hits for their site). You've now spent time building, making sales calls, etc. to earn ~$20. You now also have to get 20000 impressions to these jokes. Since odds are that the business owners go the quick route and just nab a popular joke from another site (copied content, google doesn't like that) you're not going to have high rankings and are in direct competition with large humour sites that everyone knows by name because of their high brand recognition.

Point being: regardless of price points, CPM, what business advertises, etc. it's highly unlikely that you'll get large amounts of people looking for jokes traffic as well as business looking to advertise this way. Don't get me wrong though, if you want to build it then do just that but do it because you want to or keep working out some of the kinks until you have a strong model. At this stage though it is not really a 'business' and is a flawed model when it comes to CPM prices and potential revenue.