The writers guild of America is offering opportunities of Documentary screenplay contract. The contract is designed to meet the demands of the documentary film business as well as ensure the rights and benefits for writers of theatrically released documentaries budgeted at $1.2 million or below.
Now writer-directors and writer-producers can work under the protection of the WGA without having to pay writing fees upfront. Also, theatrical documentary producers may hire writers under a WGA agreement by allowing for partial deferments of writing fees in accordance with various budget breaks.
Find more information here http://www.wga.org/contracts/contracts/other-contracts/documentary-screenplay