As noted by another response, it depends on the state. In Washington State, the moped needs to be titled and licensed, and while you are not required to have motorcycle insurance, there are financial responsibility requirements, so if you're in an accident you need to be able to post a bond of somewhere near $60K. Since motorcycle insurance is relatively cheap, when I got my 1986 Honda Elite 150 scooter I purchased insurance ($100 for a year from esurance). Insurance is one of those things that comes in so handy when you need it most. The cost depends on factors such as the area where the moped is garaged, and how many miles you expect to put on it.