Best way to structure a seller financing deal?

[Michael Fiducia]

Hi All, 

My girlfriend's father has a multi unit property in a nearby city that he has been looking to dump for quite some time. Market value is around 160k. There is a mortgage of about 100k on the property. He gave me first crack at it a while ago but I politely declined. Now that I have run the numbers, I see it can cash flow pretty nicely. 

However, I am looking to obtain a mortgage on a primary residence in the next 6 months or so. I don't want to drain my cash reserves in a big down payment that can go towards my primary residence. 

I wanted to offer him an option of selling the property to me via creative seller financing. Can anyone offer advice as to what has worked for them in the past w real figures? How much down? What interest rate did you obtain? etc. 

Thank you in advance!

Mike