Mixing conventional and seller financing terms

[Darsh Patel]

I am analyzing this deal and am trying to figure out the funding for it. The property is 200k, rents at 0.7-0.9% for the purchase price, Owner/seller says, he will finance 100k with 7.5% apr 30 yr Amortization, 5yr balloon paymt. , owner/seller needs 100k for down payment though, another potential benefit is if my credit runs okay then the interest rates drop to just 4% for the same loan financing. 

I have 20k saved up, can i get a bank mortgage for this said property, with a loan value of 80k and 30yr amortization.  My plan is to refinance the property when the high interest rates go away in year or two (hopefully) to repay the owner/seller when the balloon payment is due. 

I have a few questions: 

1. What is the general owner financing loan rates in your markets ? I was evaluating to buy even if the interest is at 7.5 apr for me since the rent and other factor work for me.

2. Do bank even loan money like this, Is this arrangement even permitted by banks for conventional mortgage? I don't want a personal loan because then my numbers just won't work.

3. Is it possible to have no money down for the 80k bank loan, that would be a dream scenario where the levarage is extremely high but i get the property with pretty much no money of my own. Have any of you even gotten a loan like that?