It seems your main concern is that it can't go more than 20mph in Arizona, or else it has to be classified as a moped, and needs licensing. No power rating, other than if it's gas-powered, it has to be limited to 48cc.
https://en.wikipedia.org/wiki/Electr...e_laws#Arizona
If it's anything like around here, a new electric bike will cost you as much as a half decent 10-year old car. On the other hand, you can pick up a used one with dead batteries for a couple of hundred, and throw in new batteries for another couple of hundred, and you're off to the races. Or a grand if you go lithium.
I'd think finding a 500w+ one wouldn't be too difficult.
OTOH, if you don't care about burning gasoline, you could probably get a used (or even new) "moped"/scooter for less. Get the right one and you'd still get 100mpg.
PS: You could probably pick up an electric conversion kit for a bike for two or three hundred, and just have to source out some batteries of your choice to go with it.