yeee, but how many bitcoins in average.
Bookmark this link
and use it to calculate how many bitcoins you'll make on average. Remember that this will change roughly every two weeks, as difficulty changes.
Use this site
to convert from bitcoins to US dollars (the site itself actually lists pretty much every exchange there is, so if you're not interested in US dollars then you can find an exchange in your own currency. The site also lists current over-the-counter deals on bitcoin-otc, which handles pretty much anything you can think of - any currency, and a fair few non-currencies. Whether the deals will materialise will depend on demand, however).