Seller Financing Help - No Interest Periods

[Glenn Jones]

Hi - I'm working on options for a commercial purchase where I'd ask the seller to hold a second position along with my SBA loan.  Due to the rates going up so fast I'm hoping to make the deal work by having the seller hold 20%.  I'd like to have him hold the loan for 10 years amortized at either 25 or 30 years.  I'd like to ask for 2 years with no interest.  How do I calculate the monthly payments and do the amortization schedule?  I have found plenty of online calculators but most only have an interest only option.  

Thanks!

Glenn