I'd recommend going to a local bike shop that has a good reputation. You should be able to get a decent bike for somewhere around that. There are so many kinds of bikes, just about any of which would "do" for a 3-mile commute, that you could probably benefit from being able to try a cross-section of bike styles and talk with someone who could help you sort out your priorities. Then, when you decide on the kind of bike you want, you'll need help getting a good fit, both in frame size and handlebar/seat height and angle adjustments. Especially when you are just embarking on a new venture like this, it's worth getting the guidance of someone with both experience and inventory. FWIW