I picked up cycling again at 50, and have ridden consistently, sometimes intensely, for the last 12 years. Had not exercised in years and was 20+ pounds heavier than I am now when I started. Some good advice upthread, some I disagree with. My thoughts:
-Stay away from "cruisers" with their substantial weight and wide bars. They are built to a price, might be fine as a rental for a tourist for a few days. Not the kind of thing you want to hop on every day for 30 minutes+
-If you're looking only to exercise, don't spend the money on an electric, just pedal. You're in the flatlands of SE FL, so there is only wind, no hills. Pedaling against the wind is good exercise. Just don't get too far west before you turn around. Or just ride N/S.
-If you're looking to exercise and become a part of a social group of cyclists, go electric, but don't be cheap about it. The assist will allow you to stay up with the more experienced folks as you're starting out. You can forego the assist as your fitness and experience improves.
-Agree with the recommendations to get to a quality bike shop. By "quality" I mean someone that sells to locals, doesn't have a big rental business for tourists and carries brands such as Trek, Specialized and Giant. All three of those companies sell a wide variety of bikes.
-As to type of bike, agree with the recommendation to look at "comfort" bikes initially. I started out with a "comfort" model and quickly moved to a skinny-tire road bike. Still have both. If I were to do it again, I would by a "hybrid" as the first one, but not everyone takes to it like I have (almost 10,000 miles on skinny tire road bikes).
-As to gear, yes, padded shorts or underwear help a lot. Don't skimp or think a heavily padded saddle/seat will be "good enough". It takes a while for those tissues to harden enough to be comfortable. Even now, I'm only good for an hour-ish without padding, and if I'm off the bike for a week, even that gets uncomfortable.
I'm glad to see any one look seriously at cycling for exercise and socialization. It's been a live saver for me physically and as a way to keep my head through professional and personal upheaval. Maybe it will be that for you, great that you are looking for something like that.