If you are going to do arbi I suggest looking at the Google content network. It is much more difficult getting large numbers of impressions from the second tier engines unless you are in highly competitive markets and even there prices are climbing.
You may need to test a whole bunch of campaigns before you get a winner. Once you do, you can get 10's of thousands of impressions for .01.
Unless you have volume you will need a lot more campaigns. The content network is the only one I've found with the most volume in many niches.
Only once you have that volume can see decent profits from 2 to 3x+ ROI off a single page or campaign.
A good target to shoot for?
-CTR of 1 to 5% on Adwords
-getting a CTR of 25%+ on Adsense
Let's say you have 64,982 impressions at a 5.47% CTR on your Adwords spend at just over .01 average. Your cost is now $41.08/day
Now let's say from those 3559 impressions on your Adsense page you get a 31.94% CTR. You have 1140 clicks on your Adsense ads. Let's say you get paid an average .108 for each click. Revenue is $123.31.
You've made $82.23/day, 2x your investment.
Why the weird numbers? It's based on a live campaign I'm running right now. I grabbed the numbers off my report pages.
So it costs you $1200 for the month but you get back $3600.
The problem is you may need to test a LOT of campaigns before getting a winner so it may take you 2 full weeks of full on launching campaigns to find a good one. On the other hand, you may luck out like one of those ebook authors and find a super profitable niche right off the bat.