Decline sorrowfully that you just aren’t in a position to take up such a “great deal”. Go with the advice to offer to stay at a lower rent while he sells. Mention that the landlord has the right idea: there are companies in California that line up tenants to house sit otherwise vacant properties who pay a few hundred a month in rent to keep the places occupied while being sold. Agree with him that he should sell soon anyway at that price. Especially if he doesn’t have to centend with the “vacant house – must be a desparate seller” phenomenon. Given a rent reduction, you won’t mind keeping the place looking nice for buyers and putting up with showings.

Point out that occupied dwellings have much less chance of burglary or other mischief. I’ve also been given to understand that standard home owners insurance does NOT cover a vacant home.