Any photo project needs to have a mission statement. This will allow you to develop your project into a coherent body of work. This mission statement will be able to be used if and when you are seeking funding and also keep you on track throughout your project. Once you have completed your project it will form the basis of your artist statement that will accompany the images when you exhibit your images in a gallery or it can become part of the forward or statement in the front of any book that you may produce.
I would suggest that you take your time to write the project statement as it will frame your project and help to keep you focused and on track when making the project.
Writing your mission statement is the 1st step in creating a plan of action in your project. After which you will have to get down to the reality part of your project. That is exploring such matters as costs, timings and considerations of the scale of your project. The project will inherently change over the lifetime of itself, however without the mission statement it will change beyond all recognition and not allow you to develop and grow through your project. If you think of your mission statement is something likeable roadmap, or outline of where you want to go, it will also remind you of your starting point from whence you originated your project. This is quite important, especially if you are using your project as a process for growth and development.