Is it a mortgage loan or a land contract?

If you're the lender you simply report it "as if' you'd received a 1099-INT.  As you say you inherited the asset I assume you're not really "in the business" of lending money.  ("Mortgage loan or land contract" is irrelevant; the borrower reports the interest deduction, you report the interest income.)

Tom Young

It it's a land contract, didn't he inherited the deed?

A land contract means that title won't pass legally until the loan is paid off.  But the IRS is clear that the reporting of mortgage interest and expense is still done "as if" title had passed.