This time of year, it may be difficult to fly a dog in cargo across the country due to cold weather, but if that can be worked around then the dog will need to see a Vet and get a health certificate (and rabies vaccine). Cost depends on the size of the dog and the crate, how big is the dog? Should be able to fly an average sized 50 pound dog for around $350. Is your friend considering flying out and meet the dog first?