Buying a 4 Plex with no Appraisal? Risk

[Mark Welp]

I am looking to buy a 4 Plex through owner financing.  C Area and cash flows really well.  Not going to get any appreciation, which I am fine with.  Seller is fine with Inspection, but wants to sell with no Appraisal (as we are doing owner financing and no bank involved).  I would have to refinance at the end of the 3 year balloon.

I know there are risks with not doing an appraisal, but do a lot of people buy like this? Any easy ways to see what the value would be (obviously I can use the income approach).  Thanks for responding and assisting.