Current Average Interest Rate For Seller Financing a Rental?

We are working on a deal right now to but a 4 plex and a couple duplexes all from the same seller with him carrying the financing. We are almost all settled with doing a 5% interest rate, 15-20% down and a 25 or 30 year amortization with a balloon at 15 years, with an option to extend that IF both parties agree.

The seller threw out a 4-5% rate and 15 year loan. The cash flow is REALLY tight at that 15 year payback, so I countered with "let's do the 5% and extend the term".

We have known each other a little bit for years as we are both in the construction trades with great decades long reputations. The feeling I get is that these are all paid off or almost paid off, and he is looking for; to save realtor fees, to have a reliable income stream to compliment his other investments, spread out taxes. I think another concern of his is finding a buyer that he knows keep things in good shape in case he ever needs to 'foreclose' on it.