You probably know this already, but you need a lot of traffic before you will make any real money.
You can start somewhere at around $0.10 per click but it really depends on the type of website and quality of the traffic. it might take 25 clicks for one conversion at best, so multiply that by $0.10 and that is what the advertiser pays to sell one of their products. If their product costs more than $2.50 they would be more than interested in your ad space, as long as you have sufficient traffic to make it worth their while.
Saying that, It can go anywhere from $0.01 to $80 per click depending on the market. The best thing to do is look at the google keyword estimation tool and see broadly where your market sits and use that as a guide.