BRRR Strategy when owner financing

[Clinton Cook]

I am looking to use the BRRR strategy on a 8 unit complex where owner financing is involved. He owns the property free and clear. I have done a similar deal in the past and I was effectively able to :

1. 10% down have the owner hold the loan.
2. Rehab the property with my own funds
3. Raise Rents significantly 
4. Refinance the whole property into a commercial loan with a lower interest rate. 

I hope to approach an older gentlemen I have a lose connection with who owns a small 8 unit complex to do something very similar, but what I have been told that the owner will likely want to hold the mortgage for 15 yr fixed period at a set interest rate and with no early pay off. He is effectively using this as his retirement income and doesn't trust the stock market and does not want to have to find somewhere to put his money but still wants to earn a higher interest rate than the bank. He also likes this idea because he will no longer have to worry with any of the day to day headaches.

I will need to renovate the property and raise rents in order to make the deal worthwhile. My concern is this. 

1. If I use my own funds for renovation. I am afraid it will be almost impossible to get a commercial loan and the bank take second position in order for me to recapture my investment in renovation. 
2. If the bank wants a first position mortgage then it is unlikely since this gentlemen is relying on this for his retirement that he will be willing to take the second position. 
3. Even if he did take the second position, I am still not sure a bank would like that because the loan amount would be now be very small. 

This scenario is still somewhat hypothetical because I have not approached him about the property yet, but knowing this desire to stay invested in the property and not having a good solution has made me question whether I could make this a win win for both parties. Since I am using much of my own capital for the renovation I like to pull this back out after renovations so I can redeploy that money in the future. It would be tough to keep my momentum going without having access to the money spent on renovations. If anyone can help me out with this or offer up any options that I am not thinking of it would be greatly appreciated. 

Thanks in advance.