• About $11,800 in the first month
• About $5,770 in the second month
• ...continues to decline after that

* Assumes you started mining at 1000 ghash/sec on October 1 2013 (24 days ago)

You did not ask about profit after your cost to buy the ghash/sec

Try various mining calculators to figure it out - here's one: http://mining.thegenesisblock.com/