It's possible, it's been done in the past and still probably works. The only thing is that it works on the long term with a lot of traffics so you have to have money to invest. For example you could pay 20,000$ for adwords each month but generate 25,000$ in AdSense. There's a lot of work to do to find the right niches and it won't work if you only have something like 30$ per month to invest.
like eben sez, it's possible.. and a lot of people have done it in the past (and probably still).. it's called arbitrage.. but it's full of risk, especially now that Adsense may ban your account if you use Adwords to drive traffic to a 'spammy' site, which is really the only way you could make any money from Adsense. Imagine running-up a $10,000 adwords bill, only to find that your Adsense account, and your $10,500 balance gets banned - and you lose all that $ .. Way too risky for my yellow-blood..
It would seem unlikely. If you find keywords that are cheap to buy that would relate to your site then logic would dictate that the ads on your site wouldn't pay much since the content on your site is related to cheap keywords.
Thats true Squat. Plus you may get the traffic there with adwords but there is no for sure way to say that the people will click on your ads. Very risky unless you have a huge budget. Its all about putting in the time and work and getting original content on your website. It will all come then over time!
It's quite difficult to do these days. Back 3 or so years ago I was making 30-50K a month doing arbitrage. Now I rely on organic search traffic. Too many people got into arbitrage and ruined it. Google cracks down on it pretty hard now. I wouldn't risk the money outlay to test it anymore.
It's called arbitrage and it used to be really easy. But now there really are very few keywords for which this could work