Do you think you have proper skills to be a good marketer? If you consider yourself to be a good marketer, then maybe you can make some money because of that. How about writing Google AdWords Ads for people who do not know anything about proper marketing? The ads are only three lines long, so there is not a lot of work involved and you could charge, let us say $10 per a properly written ad. You can find customers by looking at their sponsored results in Google, and if you feel that you could write a better ad, contact them, and they might be willing to sue your services. Webmasters spend a fortune on AdSense, and even if they pay you $10, this money is usually a fraction on what they spend on advertising.
If you are trying to advertise by using AdSense yourself, then you should take your time to write a thought over ad. This is very important because potential visitors to your website are going to decide whether it is worth visiting it just by reading your ad. It has to be concise, yet it has to draw attention. It is not that easy to advertise just by using AdSense, but if you know what you are doing then you can be quite successful.