I agree, for $100, you'll be getting an entry level bike at a discount big box store price.
If you find out you really enjoy the sport, then invest the money on a decent bike.
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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