I would just like to add that if you seriously want to commute, you will be spending lots of time on a bike, and buying several good pairs of shorts really is worth it. I commuted short distances for years in regular clothing, and in my single pair of crappy bike shorts and wearing worn-out trainers, and sure, it worked. But once I increased the distances and times a bit I started getting chafing, got some better shorts, clipless pedals, and never went back. I now have 1 pair of jeans, but at least six pairs of shorts

It's an investment in comfort and ease of washing, and no more expensive in the long run. Think of it as getting a new job, one that requires investing in swankier clothing