The minimum requirement is some sort of access to your Drupal database. For security, we’d prefer not have access to your live servers so a compressed MySQL database dump file of your Drupal site is ideal. If you have no-one to create the database dump file, we can create one on your behalf by logging in to your MySQL control panel or database server.
In the cases of large databases, we’d need to work directly on your server since transferring dump files of many gigabytes is impractical. A good practice would then be to clone the database and give us a separate login to the server. That way we won’t have to touch your live server and data.
An admin login to the Drupal control panel on a clone of your site would be useful for fine-tuning and debugging. This is normally not necessary for the first test export.
We generally take care of setting up the entire development environment on our servers. This includes creating an empty WordPress site for displaying results and for some complex migrations, a clone of your Drupal site for analysis. If you have limited budget, you can save on fees by providing us with the development environment set up and ready to use.