I prefer to work on a fixed budget when the requirements are clear and specified. I understand that this isn't always possible - in such cases I work in small steps of pre-estimated and agreed work for more flexibility.
For fixed price projects I require an upfront payment of about 20%.
All development work will be performed on the freelancer servers which shall be accessible to the client for review. All client source code will be under a strict secure control system and will be exported or delivered according the contract specifications.
Usually the product is delivered with a warranty covering the bug fixes for a certain period of time/usage.
I'm also available on Elance: https://www.elance.com/s/gepard-soft/