Protecting my $ interest in an Owner carry flip?

[Shawn Smith]

I am trying to get creative with a recent off market deal that was sent my way and was wondering how I might secure my financial interest in a property which I would like the owner to carry the note until time of sale. More specifically, the owner and I would agree on a sales amount (165k), I would finance & complete the renovations along with carrying cost (estimate $15k) , and then sell the property at a higher amount (est $215k) ultimately giving the owner a portion of the profits (20-25%?). I am looking for a legal way to protect myself against the owner changing his mind and living in a newly remodeled home financed by my money. Any help would be appreciated. Thanks so much, Shawn.