no, you dont need do have lots of sites to earn $1000+ from adsense you can earn more than that from one site if you just concentrate on that site and work harder for this site
I actually added the ads to an online catalog of products that I am selling. In 6 months time, the products weren't selling fast enough so I started a new strategy by placing adsense ads on my site. Hopefully in a few more months, I can successfully say that the adsense is generating enough income to keep me in business.
I don't mean to brag but I was making about $4000 a month from adsense, now with the economy I'm lucky to pull in $1500/month... I own a very popular download site, much like download.com... problem is nobody is buying ads right now, on top of the adsense loss I also had over half of my recurring clients cancel their subscriptions, and my traffic numbers have not fallen at all... It's only going to get worse.
Strongly agreed, it is POSSIBLE to have your first site be a huge money maker, but a basic site, with some basic revenue is a good start. It is a learning process. My website I opened has been up for not even a week and I have already learned numerous things.