Here a very good article from Forbes describing the pitfalls and dangers of a type of vehicle purchase that is becoming increasingly popular: E-Contracting.
E-Contracting is when you purchase a vehicle from a car dealer totally online. You use an electronic signature that you agree the dealer can put n the contract, and then you pay what the dealer says, and you get your vehicle.
Obviously this type of sale is an open invitation for unscrupulous car dealers to make you pay more than you agreed or include provision you never knew about. I would never recommend you do this unless you personally knew the dealer and knew him or her to be an honest person.
There is simply too much risk, and besides, how are you going to test drive the car (something that MUST be done prior top any vehicle purchase, new or used)? Or how are you going to have it inspected by your body shop to determine if there has been prior wreck damage, or by your mechanic to determine if it has hidden mechanical issues?
This type of selling and marketing is rampant in Spanish-speaking communities.