I "owner financed" the sale of my house and collected interest, what documents do I need to provide to the buyer ?

There should have been an amortization schedule showing the interest paid each year exchanged at closing.  Using that chart you will report the interest paid to you by entering the payer's name, address and SS# on the Sch B  and the payer will report your name, address and SS# on their Sch A.   You do NOT need to issue them a 1098 form.   

WHile it's true you do not need to issue a 1098, you should still send the buyer a "letter is lieu of 1098 - Mortgage Interest Statement" that provides them the total interest paid in the tax year, along with identifying information about the loan the interest was for, and the SSN or TIN of the person or entity qualified to claim it.