Hello,
I am one of the "preferred freelancers" here in mobile phone (iOS) category and since I have worked on iPad and iPhone image editing apps in the past (working on one right now aswell), I might be able to turn your requirements into a finished app.
1. Straught line - okay
2. Draw lines - this will be free hand drawing right ?
3. Shapes (rect, circle) - okay
4. Text - okay
After processing photo via each step, user will then have the option to save it to photo albums (after a preview) and then mail it to himself or someone else.
Can also add social network sharing if needed.
The milestones will be based on each features, so after initial 50% milestone deposit, it should be released once the prototype version of the project with all features is done and shown to you, and approved by you.
After that you need to deposit 25% milestone, to be released after pre-production version of the app, with tweaks, polished UI and ready for deployment. The last 25% milestone is supposed to be released once the final app is polished and ready for deployment, tested on your actual device and project is handed over to you, i.e. you are satisfied with the work.
The estimate time I think this should take is 10-15 days but I have bid for 30 days to include any delays or unexpected events, its better to ask for a few extra days for deadline and deliver earlier then to deliver something late then on expected time.
My preferred freelancer badge speaks for my quality.
Regards