i would like to see you actually get 500 domains then work on then one by one, well unless you are going to hire someone. Don't expect anything if you are just gonna put a few articles initially and that's it and hope to get easy money.
For Google, for AdSense, no site is too many, right? But otherwise for you and I running 500 sites, unless you use some kind of automated technique, is undoable
i got plenty of websites, i have an SEO team and some OGT from schools which i currently trained..it is possible..just depends on how it is done in a real world..im lucky that my place has a low cost man power..maybe i will offer outsourcing someday..just contact me if you need I.T man power..