if you plan on never transporting any people or things and are going to live where it never snows, a motorcycle might be a better idea. otherwise, your best bet is to get a car and a bicycle.
can you put everything you want in a backpack? Because that is all you will ever be able to carry on a motorcycle. Motorcycles are only dangerous if you do dangerous things on them.
if you never plan on transporting people or things, and you live in a city, and have no wish to not live in a city, then ride the friggin bus. cars don't belong there. two wheels though, can be equiped to carry two backpacks. three if you're also wearing one. they ARE much more efficient on resources (unless you put a huge engine and try to make them as wasteful as a car). just not very useful for trips to the lumber yard. and you can take one passenger, if neither of you take anything else. there IS a picture i saw somewhere (probably photoshopped) of an extended two wheeler with multiple (in line of course) seating. i think it was probably on here that i saw it. not sure how many years ago. sometime in the last five though. i think.
Think we need to know what your needs are to be of help, what would you use it for most, long trips or just getting from A to B etc.
If you’re graduating from college you could use the money to pay down your debt, if you’re graduating from High School and don’t intend on going to college; Buy a shit box for a couple of thousand and the rest on Hookers and Beer Hotwater
if you live in a city, save your money and ride the bus. if you live out in the woods or desert or what have you, you're probably going to want something you can haul a ton of crap with. because that's something you're probably going to be wanting to do, at least occasionally. so there's not a whole lot of utility to two wheels, unless, you want something economical just to ride around on and go exploring. for poking your nose into poorly maintained back roads and trails, that's where a relatively small and light weight two wheeler is hard to beat. you can get into and out of places four wheels just won't fit. (like anything else, top spec depends on what you want it for and what you want to do with it)