Creative financing question

[Matt Parker]

I have a potential property I could add to my portfolio with some creative financing. Let me know if this seems doable. I want to ensure this is legal before I put dollar amounts to the offer:

Seller still owes on the mortgage for the property so seller financing is not doable. Seller wants to keep the passive income, but doesn’t want to manage the property anymore. I pitched a “subject to” type option, but with seller financing type terms. I would take over the mortgage payment, but pay an agreed upon dollar amount above and beyond the mortgage to ensure he gets the percentage return/monthly cash flow amount. We would determine a date for a balloon payment where I would refinance the property into my name.

Is this something that can be put into a contract to ensure all parties are held accountable for the agreed upon terms?

Any advice is appreciated! Thanks!