Bottom line is what you don't want to hear. Real mics don't connect directly to computers. There are cheap USB convertors, such as B.L.U.E. Icicle, but the cheap ones don't have headphone jacks (which you will need), and their preamps usually suck. The cheapest interfaces are about $100 and generally suck also. Here are a couple of pretty good entry-level interfaces:
Best of luck. Just remember this- whatever interface you get, make sure it provides "phantom power", and remember- if you don't get at least 2 channels, you'll be kicking yourself in the ass very soon.
