Help! A walk-thru of seller financed deal

[Eric Roloson]

Seller is willing to carry a contract for 5 years. We agreed on the purchase price of 60k with 6% interest for 5 years. Smaller down payment to cover closing costs (negotiable). Balloon payment at the end to pay off or renegotiate for longer contract. Does not need more than $600 dollars a month for payment. 

This is my first time writing up a contract. My first deal was purchased off MLS and handled by buyers agent. The last was an all cash deal that was cut and dry. I'm a bit nervous as I have not done one of these before. Trying not to feel like a noob, but have to admit I'm new to this. How would you write this up (I'm in WA state) that protects me and gives the seller confidence it is being done correctly?

The plan is to close at a title company. What is the best way to lock this in and close quickly? I'm open to suggestions from those that have good ideas :)