Online your Adspace might be worth $10. a month beating the pavement to the local community your adspace is probably worth 100. a month
Most online businesses don't have a clue as to what space is worth but rather pay based on the individual so go to people who know you.
At least that is what I have noticed over the last several years around here.
Local businesses by adspace off local people whether they have business or not! That is a fact! They think that if you are online that you have millions of visitors. They think this because they don't understand the net and probably never will.
I personally have never bothered to beat the pavement but I have checked into what other local site are selling space for and actually do sell that space to the unknowing business people.
Check your site ranking at:
http://www.Alexa.com
Links and Search engine saturation at:
http://www.marketleap.com
For that matter start checking everyone you knows site ranking to compare, it will open your eyes!