I'm an outside observer, having never used this but I'd guess it's a fairly straightforward real estate loan. Disney probably has a partner bank that works with them. You could also use your own bank if you wanted to. Someone correct me if I'm wrong, but I just don't see any way they could require you to use them if you want to finance the purchase. I'm sure they make it easier and offer incentives to finance through them as they get a commision from the lender. Loan approval will be based on your credit history and score, as well as your income and your current debt to income ratio.
I assume that until paid off, the bank will be a lienholder on the contract/lease meaning that if you default they can sieze your contract and liquidate it in order to pay off the loan.