If people have nothing for collateral, they're most likely in poverty and should be receivers of charity or other government assistance programs.
So no student loans? Most 19 year olds have no collateral.
So that's a symptom of an underlying cause: the insanity of for profit college prices in the US. Other countries don't have this problem. There's also the obvious solution of giving them loans with 0% interest. Perhaps another option is to pay their tuition in exchange for working at the lender for a fixed number of years afterward.
Partnerships, issuing stock? Not exactly collateral but there are aligned interests.