At 18, a personal loan for $4,000 is not at all easy to get. It's not impossible at all, but not easy. No credit is at least as bad as bad credit from the point of view of a bank.
Personal loans are the hardest to get, because at least with an auto loan the bank owns the car and has something in case you default on the money. WIth a personal loan, they've got nothing except your word and past history to rely on.
An online bank (which I would hesitate to recommend anyways) would be even less likely to give him a loan because not only are they giving money to someone with no credit history, but they can't even see who they're giving it too -- for all they know they're giving it to some homeless bum on the PC at a local library.
He'd have much better luck getting a credit card with a $4,000 limit than a personal loan. And he'd be building some credit history at the same time. Do well and he'll have a credit card limit that he can literally buy a home with (if you were that stupid) in a few years.
I started at 17 with a $1,000 limit and by the time I was 21 I had a limit of $75,000 on my cards.
