Advice needed on potential first fix & flip with seller financing

[Sam DiNicola]

My neighbor is ready to sell his home. He is older and does not have a mortgage and there is a lot of deferred maintenance on the property. ARV $450k. Thinking of offering seller financing deal to him. Repair costs would be $150k. He is hoping to get $200k but current value of the home is more like $160-$170. We would likely take 2 years to rehab since this is our first one. But I'm not sure everything I need to consider when underwriting a seller financing fix and flip to see if this deal would even make sense. I tried the BP Fix & Flip calculator but it's not really geared toward seller financing. Would love any advice or insights. This could be a great opportunity but I'm not so eager that I would do it if the numbers don't make sense.

[Sam DiNicola]

Quote from @Jules Aton:

When I did a seller finance deal years ago on what would become a long term rental I bankrolled the rehab funds then re-financed when it was finished. Two years is a long time for rehab, did I read correctly? 

 Yes, we might end up doing it faster but I want to underwrite it with a longer timeline since this is our first one just to be safe and we would likely try to do some of the work ourselves to save on some demo and reno costs.