Welcome To Bike Forums, Cooper!

It would appear that you have the following options:

1) Monitor your local craigslist for an old 80's styled chromoly steel road bike, that's in fair to good condition. You must be patient. At this time of the year everybody's trying to buy bikes. Make ceratain the you take someone with you who knows bikes. The frame should be straight and have no rust or weld issues.
Make certain that your expert partner inspects the bike both before and after your twenty minute test ride. Get his opinion about your fit onto the bike.

If the bike doesn't feel comfortable, then don't buy it! Always attempt to get the bike for less, no matter what!

* Once you get the bike off of CL, try to join a bicycle co-op. That way, you can learn to both upgrade and maintain your bike.

2) You can just join a nearby bike co-op and try to locate a frame that will fit you. Next, you begin to actually build your own bike from the stock pile of donated parts or bicycle components. You can even purchase your own components, independently. You will then install your components under the watchful eyes of veteran bicycle mechanics. Now that's what you call, building a bike!

3) You live in Chicago. Chicago is mostly flat. You don't have any major hills to climb! Therefore, you could just as easily buy a brand new chromoly steel single speed and be entitled to a warranty.

Here are just a few recommendations for single speeds:

The Schwinn Madison ~ $275
www.nashbar.com/bikes/Product_10053_10052_540608_-1_202614

The Nashbar Hounder Single Speed~ $200
www.nashbar.com/bikes/Product_10053_10052_504148_-1_202614

The Windsor Timeline ~ $300
www.bikesdirect.com/products/windsor/timeline.htm

Good Luck!