How to Seller Finance?

[Eric M.]

The owners of the house next to me came back for a few weeks to evict the tenant and place the house on the market.  They own it free and clear.  I asked if they'd be willing to seller finance and I fumbled through the explanation of how to do it.  We agreed to both research it more and discuss later.  

How do I do this?

They did mention they need some immediate cash, no exact amount, and I proposed I could give cash up front and finance the rest with terms.  Was that a mistake?  Anyone have a script or list of questions or list ways to make the offer?