About the $100, it can seem to be daunting, especially when you're just starting, but it seems like most programs have a minumum payout, anyway. But, just because the minimum payout for some programs is $20 or so, doesn't mean that it's easier to reach. I was shocked at how much Google Ads go for. From what I've noticed, those ads run by Google seem to be worth a lot more than any other ads I've been able to find. If you make 5 times as much per click with these ads than you do with other ads, you make the "cash-in" minimum in the same amount of clicks, even if the minimum is 5 times higher. And not only that, but but when you do make the minimum and get your money, you have 5 times as much. I think Adsense is awesome. My site
http://www.arabchurch.com/ made about $40 in 3 months. Then I started displaying ads on another site of mine, also, and in less than a week, I'm at $140, so I should get my first payment this month. It all depends on which ads you display. If you want to display ads on a site with keywords that go for a very low amount of money per click, it might be better to have different advertising on those sites, but if your keywords are halfway competitive, those 20+ cents a click will add up quickly.
Rick