Buying a car in the USA

[One More Solo]

Sometime next year (around May hopefully), I want to spend about 6 weeks travelling in the States, doing the full coast to coast thing. Since I'm 18 hire companies won't touch me, so I'm thinking about buying a car there (probably in NY), driving it for 6 weeks, then selling it at the end of the 6 weeks. Obviously there'd be a fair bit of depreciation in the meantime but it should be pretty cost effective considering the cost of hire.

So, what do I need to buy and drive a car out there? I assume the UK license is sufficient. Can foreign nationals buy and insure cars?

 

[One More Solo]

Done some looking round and it is looking difficult depending on how long I plan on staying. I see that there is a decent travel pass available for the Greyhound buses though.