Before you buy a car from another state, check your state's emissions standards, your state's safety inspection requirements, title and registration information, and sales tax. Most states require a form of financial responsibility or car insurance before you can title and register your car.
Most states require cars to go through smog and emissions checks. If the car has a valid emissions sticker from its current state, you should check if the sticker is valid in your state, too.
Some states don't check safety inspection requirements, but those that do require it before you can title and register your car. Others require them on a regular basis, such as biannual or annually. Often, the dealer handles the title and registration paperwork for you, but if you're buying from a private seller, you need to do it on your own.
You likely need to pay state sales tax to your home state if you're buying a car out-of-state. The dealership usually handles this for you, but if it doesn't, or you buy from a private seller, you need to pay it in your home state before you can title and register it. Remember to keep the records to show your state's title and registration office if the dealership handles the process for you.