the landlord took the risk, could have been $0.
second hand restaurant equipment can be bought at a discount. food suppliers offer credit, 30 - 60 days.
if you are willing to put in the work, there are ways to get started other than borrowing money from a bank.
The rule of incorporation in the US is to minimize the cost of failure to the individual.
> and negotiated a 5 year lease for a percent of his gross sales.
> the landlord took the risk, could have been $0.
Gross sales. That's sales before expenses. Your brother-in-law took on literally all the risk in this scenario. Unless the zombie apocalypse started in that very mall, any store was going to sell some burgers and your brother-in-law was going to be paying out to the landlord before he had covered his own costs.
Note that you can buy in via personal debt, but that is not “leave with nothing”.