I didn't buy a car until 6 years after I passed my driving test. I was living at home, going to school and simply drove one of the family cars. I found the first car I purchased in a newspaper classified ad. Just for the record, that was 42 years ago and I still own that car. (I've had a lot of other ones since, though.)
I've only purchased one car on the internet, through Ebay. I had been looking for a specific antique car and found one close to me. I have done a lot of research before purchases, generally sites like KellyBlueBook and manufacturers' sites.
Driving advice wasn't an issue for me. I was a gear-head long before I could drive, so it was like a duck taking to water for me.
Who would I approach for driving help in the absence of family or friends? Not a question I've ever asked myself. I suppose that I'd have to find some sort of school or training center.
How would you feel about a company introduced to the USA who were dedicated to helping first time drivers?
I suppose that it could be made into a workable business model. The catch is that becoming a licensed driver in the U.S. is such a different process than it is in Europe that it's difficult for me to imagine how many young drivers might want to use such a service. My guess is that the clientele pool would be very limited.
My answers probably aren't typical - or the ones you hoped for, but I hope this helps with your project!
Dave B.
Southern Ohio, U.S.A.