$8mil MF portfolio, seller finance, what interest rate?

[Kelby Schimming]

BP, 

I am working on a deal in Texas, and I have found an off-market portfolio that the seller is willing to finance. 

I've done some underwriting, but I am caught up on what interest rate to start negotiations with. 

It seems the price is most important to seller, he is motivated to sell, but doesn't have to sell. 

Any suggestions or starting points for interest rate negotiation? 

 I don't want to come in higher than I need to, but also don't want to get laughed at for coming in too low. 

I am also motivated to get the deal.

Any feedback is appreciated. 

Thanks in advance