Do you have a bike already? Then, whatever it is, use it. You'll know soon enough if it's suitable or if it needs modification or accessories.

I started a thread in the Classic & Vintage section called "What's in your tool kit?" or something like that.

There are tons of threads which answer your questions more extensively than you'll ever want. Just take a good length of time to read them. There are also blogs on bike commuting.

Welcome! It's fun. You'll find that bike commuting saves time over driving+exercise. Cycling to work takes less time because you're doing two things at once. The time-cost for me to cycle to work is about 30 minutes, and for that cost, I get a 60 minute workout.