I have a deal.. What's Next? Seller-Financing

[Jantsen Locke]

I have a seller who is interested in selling their single family home, and is willing to go the seller financing route.  I have ran all of the numbers and I think this could be a good deal.  

How do I make sure that the contract is written up and executed in the correct manner?  Would i approach a title company, a real estate lawyer or attorney?  

What is my next step?  Thank you in advance.