Moved it for you, and I salute you.
The advice above is sound, the only thing I can add is to go ahead and buy one of those $25-100 bikes. Start riding around the neighborhood, only like 10-15 minutes per day. Start 3 days a week for a month. Then increase by one day every couple weeks so you're riding 5 days a week. Every week after that, increase your time on the bike by 5 mins.
The key is to start out slow and don't overdo it. If you do, you'll burn out and it'll become a chore instead of a pleasure.
If you do this, in no time at all, you'll drop the weight, increase your stamina, and find out (inexpensively) if cycling is for you.
I kinda know what you're going through. I've always been a "BIG GUY" and this last year, my wife was sick and basically bedridden, and I put on the lbs due to stress and lack of "Me" time. This Aug. I was the biggest I've ever been tipping the scales close to 300 lbs. I've been on a low-carb diet and try to ride about 5 days a week. In 3.5 months, I've dropped 25 lbs and my goal is to drop another 10 by Christmas.
The key is to not go psycho and try to loose it all at once. Pace yourself and you'll be successful.
L8R
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"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
"Your Bike Sucks" - Sky Yaeger