Need help structuring seller finance deal

[John Schaffer]

Hey BP,

So my grandparents have been trying to sell there house for a few months now. There is no mortgage on the property. They have already moved out and are living with my aunt and uncle in an in-law suite. The house is in excellent condition in a great neighborhood. Buying this house never crossed my mind because it is so far out of my price range. But after @brandonturners most recent webinar, he said to take action. So I listened to his no and low money down book on audible.com. After listening to the chapter on seller finance a light bulb went off in my head, I grabbed a piece of paper and started to throw some numbers around. 

This is my plan. The house is currently listed at 300k (appraised at 350 but recently dropped asking price). It needs some minor updating remove wallpaper, paint, new light fixtures, and possibly update master bath. I would pay for those minor renovations out of pocket, with my own labor. With these updates I am confident I can get the ARV to around 400k.

Now to the seller financing structure:

purchase price- 300k

taxes- $900

insurance $100

Over 5 years (60 months) make monthly payments of $1,000 (60k) 

(Assuming 0% interest and 0 down payment being the wonderful grandson I am)

I attempted to use the rental property calculator to analyze but this deal is a little out of the ordinary.

After those 5 years do a cash out refi to pay back the remaining 240K and assuming it will be valued in the 400k range I could pull out some more equity to buy more properties.

I plan to do the renovations within the first month and getting renters in there asap. Similar houses in the area rent for around 2,300. After I update I am confident it will rent for 2,500. Leaving me with $500 in cash flow for the first 5 years!!

I would really appreciate any feedback or direction if I am missing anything. This would be my first deal and put me on my path to building my real estate empire!! 

Thanks BP you guys are awesome!!