Am I crazy for asking this?

[Kim Durst]

I just signed a purchase agreement yesterday, $305k. The seller is financing the deal until I sell my other home. We are hashing out interest rate and terms. I am interested in an amortized 30 year term with a 5 year balloon. Seller has offered this at a 5% rate all the way down to 4.5% depending on how much cash we put down.

Here's the crazy  questions/statements......I want to pay LESS interest. I'm feeling under education in this arena and wondered if someone may have a great negotiating strategy. 

My goal is to try to pay this loan in full within the 5-10 years, depending on what my current home sells for however, I need the protection of a 30 year term payment just in case. What can I present to the seller today to sway her to consider lower or zero interest? She is open to negotiations.