Don't spend too much on a bike to get started, especially if you're not sure you'll continue riding. I resumed cycling last year after a 30 year break with a $120 used bike from craigslist. Still riding the same bike, still enjoying it.

Ride on the *unoccupied* sidewalk if you're more comfortable with it, especially in dangerous street zones. Just be extremely cautious approaching parking lots, driveways and curb ramps. Cars aren't looking for bikes. And don't crowd pedestrians if you happen to encounter any. In my area hardly anyone walks, so when I was still struggling to get back into shape last year I rode some sidewalks until my conditioning improved. There are still a few tricky areas where I'll still detour onto sidewalks or parking lots for 100 yards or so.

It'll probably be harder than you anticipate at first, especially with the tension of riding in or around traffic. Stop and start riding can be exhausting. You'll begin to notice even tiny hills that you never noticed before while driving or walking. Try to use your days off to get into shape, at least for the first few weeks. Find a hilly route and ride it repeatedly until your legs and lungs are on fire. Rest, repeat. Even 15-30 minutes of this once or twice a week will help. After a few weeks or months you won't need to work yourself so hard just to stay in shape. But it'll hurt a bit for the first month.

And get some puncture resistant tires, maybe sealant filled tubes as well. Avoiding flats beats fixing flats. For most rides under 10 miles on relatively flat terrain you won't notice much difference between heavier puncture resistant tires and anything else.