As you bike you will determine your preferences. What you are riding two years from now may be a completely different type of bike than what you are looking at now. My suggestion is not to overthink anything right now. I would go to Craigslist and find a used bike for under $100 in good working order, with rigid frame and road tires (since I assume your commute will be on streets). As you get to know your preferences you can add things to the bike- ie rack, fenders, lights. After you have a good idea of the bike you want then go and make your new bike purchase. The accessories you have added to your craigslist bike you can remove and put on your new bike.