This is an easy job for the right people.
1. You'll sign an NDA (per our clients requests)
2. We'll give you 5 to 10 very similar assignments to start
3. You can bill us your regular hourly rate
4. Based on our experience and yours on the first 5 to 10 companies, we'll agree to work together further (or not)
5. You'll tell us an average cost per project for similar projects (and a reasonable bonus for same day turnaround)