Is this an installment sale, or contract for deed or Rent to own?

You would not be able to insure something you no longer own.

You don't pay taxes on something you don't own. You sure don't write off the tax expense when it is not your taxes.

Perhaps he is passing on the tax and insurance portions, so that he knows the property is not at risk of loss or tax sale, because he sold it as installment, and doesn't want to lose the secured property? Or, he didn't bother to lien it?

And the installment sale will have principal and interest, of course.

I think some of this needs to be clarified.