A propane generator will not buy you much time or output.

If the home owner has natural gas? They should could get a natural gas generator, that way they have a continuous supply of fuel if the grid fails.

Grid and gas failure? That happens only after a significant event, like a major earthquake. Not much you can do about those sorts of events. ( The person lives in Ohio… so not as much concern. )

Cost-wise? They would be better with a dual fuel system for heating. They live in Ohio, they probably have AC so moving to dual fuel when the AC system needs to be replaced is the smarter option.