Once you get to the top, you can basically leave it alone. Searches will remain roughly the same each month (with exception based on product type, November and December will likely bring in more business), a certain percentage of visitors will make you money, and you likely won't have to touch it again for years to come while earning a regular monthly paycheck. I talk to people making $10,000 and even $20,000 per month with this method, but these guys have been doing this for several years.
What this involves is making a website with keyword rich content. Basically, you need to learn how to write articles that Google likes. This takes about 10% of your time. Then the other 90% of your time is spent building quality backlinks to your articles. This usually takes the form of submitting article rewrites to article directories which get indexed frequently by Google and up the relevance of your page, although several other factors come into effect such as your domain age, site relevance, and most importantly, similar searches.
I am a member of The Keyword Academy which focuses solely on this method. It costs about $30 per month and they have several tools which make the process easier. One tool they made is called Niche Refinery, which takes thousands of keyword results from Google's Keyword Tool and identifies which keyword phrases are worth pursuing by looking at traffic, cost per click, and checking the page rank of the top four pages for that keyword (one of several difficulty indicators).
They also have a system called PostRunner, which is basically a network of article directories that members control. This is different from other article directories in that they have strict quality requirements. Since the article directories are run by members (you can add your own to the network), they are often ranked better in Google because the members know the tricks of the trade. Basically, this means that your backlinks from PostRunner are better than many other kinds of backlinks you could be going after. You