You can see here what the ROI is for the various ASIC mining devices:
http://mining.thegenesisblock.com/Select a machine under Market & Hardware Parameters
Then on the left you will see the expected payouts.
It's not looking good except for the fastest miners (400 GH/s+).
And those are all on pre-order. You can't tell when you can start mining. The longer it takes, the less you will make. You may not even break-even.
![Sad](https://bitcointalk.org/Smileys/default/sad.gif)