Scooters are fun, they're efficient transportation, & they ease traffic congestion by taking up less space. They're also easier on the roads since they're lighter. I started out on a 125cc scooter, & have moved to larger displacement motorcycles. Now I spend most of the time when the roads have no salt getting around on 2 wheels & loving every minute. Over the winter I'm usually driving a car, but occasionally get my hands on our sidecar, which is a completely different sort of fun.
The 2 main drawbacks of riding are being exposed to rain (which is easily taken care of by a rain suit), & car drivers being obliviots - they usually don't mean to try to kill you, it just works out that way because you're not in a steel cage. That can be partially remedied by taking rider safety training, wearing bright colors, and always having your head in the game - pay attention, think ahead, & expect people to do stupid things so you're ready to counter them.
"a 50cc scooter, that will travel at about 35 mph, and gets about 100 mpg."
Unless you're a small adolescent, an engine that small is underpowered. Don't go below 125cc, but for your first motorcycle don't go above about 300. My 125cc averagaed around 85mpg over 10 years & it could go 55 easily.
A tiny engine might do OK on level ground, but in real life there are hills. Traffic, too, will sometimes try to bite you & you need a bit of power in reserve in order to get out of someone's way.
Helmet - decent basic models are available for $200 or less. Make sure your helmet is rated by the DOT &/or Snell. Full-face helmets protect better than open-face. Pricier models will be more comfortable, but not necessarily protect better. (Mine cost $550, but is so comfortable I wear it year-round. I even did 19 hours in one day with no discomfort... at least not due to the helmet.) Try on different brands, as their forms are different. Some are more oval, others more round. If it fits your head, it will be comfortable & you're going to wear it.
Licensing - compared to the cost of your car license, adding this is minimal. Many states waive the practical test if you've taken safety training. Insurance agencies frequently give a discount, too.
Maintenance - much can be performed by the owner.
Outfits - a rain suit is fairly cheap, & will extend your available riding days. Don't make your first time a downpour, but don't be afraid to stretch your limits either. The first 15 minutes or so are the most dangerous, before the rain rinses oil off the streets. As it gets chillier in the fall, add layers, ending with one that's windproof. Scooters provide better protection for the legs than motorcycles.
Storage is usally fairly easy if you have a garage. Scooters & smaller motorcycles fit into fairly small areas.
Since motorcycles cost less than cars, they're usually cheaper to insure.
The one thing you didn't list that is very important is safety training. A scooter or motorcycle is a completely different animal from a car. It's not just a pedal bike with a motor, either. People who take training are less likely to be in a crash. This can be fairly cheap through the local community college; the course I took was under $200. What I learned was priceless.