How much do you spend on revenue generating websites

Hi
I would like to know how much money do you spend to maintain your revenue generating websites. How much do u spend on article writing,linkbuilding,seo etc etc and how much do you earn in return..
If you do it yourself, let me know how many hours do you spend per day to maintain your website
And how many websites do you have ?
Would like to learn the market, competition and level of efforts people put into to make money!

See original post by designventures