The mean streets of Chicago are rife with potential for pretentiousnessless creative communality and cultural thriving. Human-powered cargo-hauling action is waiting for you. Do away with the car, the bus, the train, the postal service, restaurant delivery, all of it.
Here are some equipment issues to think about: This is a relatively flat city, in case you didn't notice. That means hauling heavy loads up hills won't be an issue, but that doesn't mean you don't need gears. Starting out from stationary with a trailer full of amplifiers or a big bag full of your family's laundry takes a lot more power than with nothing on your bike. Gears are a cargo cowboy's friend, and there are options to suit all budgets and needs.
What we have plenty of in Chicago, however, are potholes and generally crappy road conditions. Blame city government or the freeze/thaw cycles of our enviable temperate climate or whatever suits you, but the fact remains. So, while you're enjoying the wide gear range that allows you to haul your crate of phat pants to the rave, make sure you've fitted your wheels with sufficiently ballooney tires that you protect those expensive rims. You might be surprised at how pleasant the ride on bigger, airy tires can be, and they won't slow you down the way you think they might. The bigger cushion allows you to float over the bumps, while skinnies will beat you up and increase the risk of rim damage. This is especially important for cargo use because you're not going to be able to bunny-hop potholes with veggies and a yellow lab in the crate.