How do you structure seller carry financing for a BRRRR?

[Ryan Monty]

I'm about to begin negotiations with an off-market seller of a property I would like to BRRRR. Because there is a good tenant in place, the current owner stated they would like to keep them around, plus I believe this would likely save me a lot of money vs. using hard money for my "bridge" financing, I would like to have a seller carry option to offer in negotiations ready to go.

As an investor, how do you structure seller financing?  What's best case scenario for the investor?  Where do you start negotiations and how do you step things closer gradually to an acceptance on their end?  How do you sell it to the seller as a good option they should go with ?

I am confused on if this financing is amortized like a conventional loan, or do you make it interest-only with a balloon?  What's a common term and rate in today's market?