> Do mortgage providers consider it enough to show a signed multi-year tenancy agreement as sufficient collateral to offer a 100% value mortgage, and therefore Neumann didn't need to put in any cash himself?

I'm pretty sure he didn't apply for a traditional mortgage through a traditional lender in the way that we plebians or even publicly traded companies do. He has a long history of using his charisma and star power to get private individuals to make completely idiotic deals that benefit him and leave them holding the bag.