You can also run a big site like hubpages, squido, or any forum

[alexpabla]

Yes, running any big site is a little hard but you have learned it well then it would become easy as well. I would say instead of creating many sites try to focus on one site it would create authority on the web and earning potential is also very high.

[BlaZe]

Well running a big website generally involves alot of things which you haven't mentioned. If you're one man army then you should know almost everything about web development.
From Server Maintenance to coding your own snippets for better functionality of your website.