What kind of loan would my retired parents qualify for?

[Mike Franco]

Retired parents have $1M liquid cash in the bank, looking to buy a $500k home with 20% down.

Clearly they have enough to buy in cash, but the plan is to use other peoples money and have the rent cover the monthly payments.

There's no income, but if banks could somehow quarantine some of this liquid cash each year, they would guarantee no default in payment.

Is there a low interest rate loan they can get?