First, it takes months or years to exit bankruptcy (at least in the US). I assume Canada also has multiple forms of bankruptcy (like the US) which includes either dissolution or restructuring.
If David's enters a restructuring bankruptcy, every creditor (including owners with future rentals out there) will get a letter saying the business is in bankruptcy and they may not get paid in the future (to the owners) or that their rental may not happen due to the restructuring and the inability to pay in full for the rental. Every supplier (including owners with future rentals out there) that is considered vital to the restructuring will get a letter saying that they are required to continue their contract, with the debtor-in-place financing paying for what would have been paid by David's. Non-vital suppliers will get a letter that says their claims will be handled under the restructuring and they may get less than they are owed. Debtor-in-place financing will keep the company in business until it can restructure its debts (often paying pennies on the dollar to non-vital suppliers), and then the company will exit bankruptcy. There will be turmoil, and some people will not get paid in full, but the business will continue.
If David's enters dissolution bankruptcy, the court will advertise for buyers within a relatively short window. If there is a buyer, a contract will be written and a hearing held where the creditors can complain about the settlement and a judge will make a decision. If there is no buyer, the business will cease, and the assets sold at auction. There is a probability that future DVC rentals would be considered a liability (because they generate no new cash), and the owners would get pennies or nothing for their future 30% payment. At that point, the bankruptcy court releases all future liabilities from the company and to the company, which invalidates the 3 way rental agreement. The owner, at that point, could walk away, allow the rental knowing they aren't getting their full payment, or make a deal with the renter.
Typically, brokerage businesses don't have a need for a lot of cash. They take cash in, keep a small amount (their commission), and then pay the rest out to the supplier. When a brokerage business sells "futures" (products paid for now and to be delivered later), they need to account (escrow cash) for those future payments while waiting for the delivery of the product. For these kind of businesses, a downturn in business does not force it into bankruptcy. What does force it into bankruptcy is when the "futures" cannot be fulfilled, and they are forced to pay back not only the escrow amount, but their commission (which has already been paid as salaries and expenses to keep the business going).