Seller Financing Logistics ?

[Derek Tellier]

For those of you that buy a lot using seller financing what structure do you start with when presenting to a seller? 
Let's set this up saying it's a $100K sale price, with about $75K Equity. 
You put 10% down leaving a $90K note. 
Would you start by simply offering to pay a flat $250/month for 30 years to give them their $90K? I know it's highly unlikely that anyone with much common sense would do but I'm willing to bet there are some out there that have done it. 

So the question is do you start there? Or is that too "risky" that the seller would just kick you out the door and you loose any shot at it? 
Or do you start with something more realistic, 20 year note at 5% interest? Do you include a balloon in the first proposal? After 5 years? 
I realize the purpose of seller financing can often be to get the seller the price they want and as long as you're cash flowing on the deal you're ahead of the game. 
Do you give yourself contingencies to balloon out sooner should it make sense to refi after say 2 years? That would of course all depend on the interest rates as it might just make sense to keep the owner financing in place if they're willing to. 

Thanks for any advice just running concepts in my head to prepare myself for negotiations.