Scope
Nobody writes code until both sides can describe the same release.
Scoping is a paid piece of work in its own right, and it is deliberately small. We go through the product, the constraints you already know about, and the ones that turn up once someone technical looks properly. What comes out is a written description of the release specific enough to disagree with.
What comes out of it
- A written scope: what ships, what it does, what is explicitly out
- The technical constraints that will shape the build
- A shape and a figure you can take to whoever approves budget
- An honest read on whether this is worth building at all
Your part
A couple of working sessions and access to whoever knows the product best. That is it.