Need guidance on structuring a deal-land contract or lease option

[David S.]

Have a seller interested in owner financing. Owes $240k with 17-18 years left on a 30 year ARM. I offered him subject-to, with him taking a carrying for $50k. Retail would be around $315k. Yeah, not a whole lot off retail, but this would be basically no money down except closing costs, and would still cash flow about $300 a month, while building $10k a year and growing in equity.

Seller isn't interested in subject-to. He suggested a contract for deed. My understanding is that the contract for deed has the same due on sale clause risks as a subject-to, and gives me less legal protections. Is there a way to structure a CFD for it to work?

Alternatively, would a lease-option work better? I could lock in the current price, no concerns about due on sale, and deferred risk for me. It still cash flows, I have nothing out of pocket, and can eventually purchase the property for less than what the market value would be.

Notes: I have enough cash to do a traditional financing on this, but would not. Putting $75k down for a few hundred a month in cash flow doesn't make sense, plus, I lose the equity gain from being 12 years into a 30 year mortgage. 

@Brian Gibbons

I've read some of your posts, and you seem to be an expert - do you have any advice?