Please help me understand seller financing and amortization

[Stanley J Okazaki]

"Terms: 20 yr at 5% interest only with balloon at 7 yrs" 

Does this means that the loan itself is for 7 years & should be paid off within this time frame? 

Monthly interest only payment amount will be based on if it were divided over a span of 20 years but only paid up until the balloon payment is paid? 

"Plan is to refinance at year 7 mark before balloon payment"

What are borrower requirements in order to be able to refinance out of a seller financing? Need a min. % of equity? Need w-2 income & good credit?