Start with a working workflow, not a feature list
A first version should prove value. That means choosing one workflow with a clear user, input data, action and measurable result.
When a team tries to describe every role, setting and report at once, the project becomes more expensive without necessarily becoming more useful.
What should not be postponed
Even in the first version, access rights, error logs, backups, clear statuses and the ability to reconstruct processing history matter.
These items do not look like flashy product features, but they are what separate a working system from a demo.
How to prepare for an estimate
It helps to collect the current workflow description, sample data, user list, infrastructure constraints and acceptance criteria in advance.
This lets the team separate must-have scope from optional ideas and propose a realistic first stage.