Take a look at http://blockchain.info/charts/hash-rate

Notice how the hash rate is increasing rapidly.

Right now on a daily basis you are getting  (60 Mhs (your mining rate) / 60,000,000 Mhs) * bitcoins mined per day right now (~3600).  

Which is your idea of free money.

However, in a month or two, you'll probably be getting half that as the hash rate increases to twice what it is now.  

If you can find a way to get an ASIC miner very quickly, you'll be good to go, but if takes awhile.. it's a waste of money.