You may have noticed that there are 49cc gas scooters for sale. So why would someone make a scooter that was 1 cc smaller than a 50cc? Well, 50cc is usually the cutoff for licensing. Any scooter 50cc and over is seen as a motorcycle by the state. The difference between a 50 and 49cc gas scooter is small. You really wouldn't notice the difference. But, with a 49cc you don't have to worry about all the stuff that goes along with motorcycle registration. You still may have some legal hoops to jump through, not every state or municipality is the same. Some states regulate motor vehicles by speed and engine. For example a bicycle with an electric assist motor that goes under 20 mph and can be pedaled it's treated the same as a bicycle and needs not extra registration or any thing. Just be sure to check your local laws to see if a 49cc gas scooter will work for you.
If you're considering buying a scooter and driving it on the road you may want to take a look at the gas scooter laws in your area. Many states in the U.S. require you to get licensed the same as a motorcycle, if your gasoline scooter is a certain size. That means registration, drivers license or motorcycle license, and all that. There might be age limits too, as well as your scooter having certain safety features.