Wow you have over 500 domain names. In truth what I have seen is that most people greatly exaggerate how much they make with adsense. Although there are strategies to make money with hundreds of domain names used in conjunction.....90% will not make you money off ads. Parked domain names usually end up burning a hole in your pocket.
As for making money with ads. Sure you can do it. As a rule of thumb per 100 impressions to your site you will get anywhere from .5% to 3% of visitors to click on your ad. Each click may get you .20 to 5 dollars (usually closer to .20).....So if you do the calculations you will quickly see that making money off ads requires ALOT of time ALOT of users and ALOT of effort. To compound that there are plenty of smart web developers all over the world trying to do exactly what your doing.
I don't mean to say any of this to discourage you, but to give you a real reality check. If you want to make money with ads online or with parked domain name it just requires alot of hard work dedication and effort.
Theres a model called porters five forces model you should check out. It shows the attractiveness of industries...industries with low barriers that anyone can do are going to become insanely ridiculous (like google ads) in terms of competitiveness. Likewise industries with high barriers that require specialized skills (say advanced programming) will have less competition.