How easy and cheap is it to buy a car in the US, and how much on average would insurance for a 21 year old be?
In Florida if it makes a difference. 

Also, how much should I be looking to spend on a phone tariff/any recommendations  I'd be using an iphone, not making international calls, but some kind of data inclusion would be good. 
Thanks!

ETA: Car wise I am looking for the absolute bare minimum I can pay, i'm happy to get something that'll fall apart once i've got my years use out of it.