I was not talking about a legal arrangement.

The law binds lenders whether they like it or not. Do you think our enforcement of the law is or would be inadequate?

Are you unaware of the existence of loan sharks?

I'm aware of some who are currently in prison, and others who have left the business (which has got a lot more competitive as legal payday lenders have got a lot more efficient). Like burglary or any number of other crimes, we'll probably never be able to eliminate it entirely but it seems to be in massive decline and a pretty poor way to make a living - and one would expect it to be even less common in a world with basic income.