Strawbunyan Start with any bike you have - and over time you'll see what you prefer.
Similar goes for clothing and other equipment.
You can't know until you start - and when you start, for a 5-mile ride, you most probably won't need anything really special.
My 2c on commuting bikes, but also clothers and other stuff:
Commuting bicycle buying guide
I-Like-To-Bike
Very good points. I agree. With a few notes:
The savings probably depend on where one lives (and how much one earns).
Fuel prices (in my country they are quite high).
Parking fees (you need to pay parking when you are in my city in many places and that adds up pretty quickly).
Pays (in Serbia they are quite low, so a $50 save per month goes a long way for many people).
Health problems prevented by cycling can be very expensive in coutries without good medical care (my country no longer has good free health care, nor unlimited paid sick leave - we went all capitalist now...).
Congested stop-go traffic and short drives can increase wear and tear and car maintenance costs.
Having said that, I agree that the
savings are surprisingly small when you account for everything (bike and car maintenance costs, taxes etc.), if the bike commuting doesn't allow you to not own a car or at least to not own a second/third car that you would otherwise. And that's without calculating any extra time spent on commutes (though in my city the traffic is gongested enough for the bike to be actually faster or at least just as fast).
Relja