What interest rate for 10% Note

[Parker Fairfield]

I'm selling a commercial property in NH. 
What's a reasonable interest rate? They've suggested 6%. Seems SUPER low. I would think that 9% is reasonable. 

Your thoughts? 

Purchase Price:

• Total: $1,985,000.
• Deposit: $10,000 (First Deposit) within 3 days, additional $30,000 (Second Deposit) within 30 days.
• Seller Financing: $297,750 (15%), 5-year term, 20-year amortization, 6% interest.
• Balance: $1,647,250 to be paid at closing.