Hi All - I have a couple rental properties but am humbly looking for advice on a scenario I haven't experienced before.

The owner of a duplex (2BR 1BA/1BR 1BA) next door to a duplex I own is 63yo, has had some back and knee surgeries and is experiencing a vacancy in the in the 2 BR unit for the first time in 15 years (and the tenant, who I knew took excellent care of the property and he was very passive).  I believe he was exploring selling before covid and his vacancy but the vacancy is increasing his interest in selling.  He owns the property free and clear and is entering his 28th year of opening so can no longer take advantage of depreciation.

I've read a bit about seller financing including this piece:https://www.biggerpockets.com/...

However, in this scenario, I'm not looking to take over a mortgage.  The seller mentioned he had another property but doesn't want to sell them both at the same time because he doesn't want to get crushed on capital gains taxes.

I'm looking for ideas of how to structure an offer to him that helps him while investing as little of my own capital up front as possible (maybe only rehab ~20k).  My initial thought is to structure something where I'd make him monthly payments of P+I for 3-5 years and then agree to refinance and pay off the balance - but have no idea what an appropriate split would be.  

As I said, the property needs about 20k in rehab, he told me a local realtor who I'm familiar with told him ARV would be ~230k. Zillow estimate is 245k and he's looking for 190k as is. Gross rents (pre-vacancy) were 1450, I believe market rents to be 1650 or a bit more. The property is in a suburb of Milwaukee (Wauwatosa) which has very strong schools and is an A/B area.

Any thoughts on how to structure something would be very much appreciated.