Listing the Benefits of Owner Financing to Seller. Please Help

[William Coet]

I'm trying to brush up on what the benefits of owner financing are for a seller so I can list them for him.  I plan to make an offer, but it will be for quite a bit less than asking price.  It's the only way the property will work with the improvements it needs. 

If seller holds the mortgage at 6% he can earn almost 400k more than asking price over a 30 year amortization period. (He may not want such a long payback period so I'm interested in hearing solutions to this issue as well). 

In addition to earning the interest on a loan secured by the real estate, what are some benefits for him in holding the mortgage?

Any ideas would be appreciated. 

Thank you