Wouldn't most of that be handled by corporations making agreements among themselves? I don't think "the entire financial system" is really based on hooking individual people on unsustainable credit.

So if I want to buy a house, but don't have enough to cover 100% of the cost in a single down payment I'm just SOL?

I guess I could rent instead, except that would require a contract as well. I get the impression you haven't really thought this through.

No, the entire financial system is based on companies being able to enter into contracts directly, rather than requiring each of their owners to be individually involved in every transaction.