Need advice about BRRRR non-conventional financing

[Joye Meinsen]

My Uncle and Aunt want to buy a house and we want to use BRRRR to start a rental business. What are the best options for using his money to buy the house, refinance and still keep his risk low? He likes to invest in CDs at the bank! Yikes. He would like the house to be collateral but then we wouldn't be able to refinance. Could the 2nd house be used as collateral, and the then the third, forth and so on? Not sure if this is feasible.??? I want to make sure he is safe financially as he is 84 and I'm sure he is concerned about the money for his wife if he was to die.