Lease Option Sale Contract

Greetings All,

If you have a tenant on a lease option to buy in two years, how do you write your own sale contract? At the end of two years, I would like to be able to write the purchase agreement or contract myself and save the fee’s using a realtor to write up the sale contract. I have found this to be 3-5% in fee’s. How do I write up a sale contract myself and submit it to escrow? How does it work? What would I need to do? What have you done? Looking forward to any replies which will help alot. Thank you in advance.